The impact of sound-field amplification in mainstream cross-cultural classrooms: part 1 educational outcomes.
The goal of classroom instruction is comprehension. In order for speech to be comprehended, the individual must be able to hear well enough to discriminate the word-sound distinctions of individual phonemes (Robertson, 2000). Normal hearing for children is 15 dB HL or better at all frequencies, and with normal middle ear function (Northern & Downs, 1991). A minimal or slight hearing loss extends from 16 dB HL to 25 dB HL (Clark, 1981). As noted by Flexer (1995), the prevalence of these lesser but educationally significant hearing losses is underestimated. Poor comprehension in the classroom is not, however, limited to those with hearing loss.
Acoustical factors affecting classroom communication
In a review of children at risk of poor comprehension in the classroom, Nelson and Soli (2000) concluded that young listeners perform more poorly in noisy situations than do adults, and the ability to listen when surrounded by noise is not fully developed until adolescence (Stelmachowicz, Hoover, Lewis, Kortekaas, & Pittman, 2000). Additionally, a child's auditory brain is not like an adult's until about the age of 15 (Chermak & Musiek, 1997). Therefore, children cannot rely on years of language and learning experiences to fill in the gaps of missed information.
The combination of excessive noise and reverberant classrooms contributes to the difficulties faced by all school children in understanding the teacher's verbal instruction (Crandell & Smaldino, 2000). Flexer (2002) referred to a national acoustical standard recently adopted in the United States (ANSI, 2002), which calls for classroom noise levels to be less than 35 dBA, and reverberation time (RT) to be less than 0.6 seconds for medium-size rooms and 0.7 seconds for larger-size rooms.
Numerous studies have found recommended acoustical standards are not achieved in the majority of classrooms (Crandell, Smaldino & Flexer, 1999). Noise levels in unoccupied primary school classrooms typically range from 41 to 51 dBA (Bess, Sinclair & Riggs, 1984; Crandell & Smaldino, 1994). Other investigations have reported noise levels in occupied primary school classrooms ranging from 52-62 dBA (Crandell & Smaldino, 1995) to 65-69 dBA (Pekkarinen & Viljanen, 1991).
Communication in cross-cultural classrooms
Adult individuals for whom English is a second language (ESL) experience greater speech perception difficulties in difl]cult listening environments than native English listeners (Crandell & Smaldino, 1994; Nabelek & Nabelek, 1994). Researchers have noted the implications this may have for non-native English-speaking children who are listening in poor classroom acoustic environments (Burnip, 1994; Crandell, 1991; Crandell & Bess, 1986; Crandell & Smaldino, 1996). Nilsson, Gellnet, Sullivan and Soli (1992) found that the ability to understand spoken English in noise is related to the individual's proficiency with the English language. When examining the speech perception of 20 native English-speaking children and 20 ESL children, Crandell and Smaldino (1996) found the ESE children's performance was significantly poorer across most classroom listening conditions.
Cultural differences, language differences and different learning styles also contribute to the difficulties facing teachers and children (Eriks Brophy & Crago, 1994; Howard, 1991; West, 1994). In an ethnographic study with Inuit school children, Eriks Brophy and Crago (1994) emphasised the peer group as being an integral part of the building of 'classroom talk', and identified the facilitation of peer exchanges as one of the most important roles in the classroom.
Sound-field amplification is an educational tool that increases control of the acoustic environment in a classroom, thereby facilitating acoustic accessibility to teacher instruction for all children in the room (Crandell, Smaldino & Flexer, 1995). Through the use of loudspeakers, the teacher's voice is transmitted from a microphone to a receiver and amplified evenly throughout the classroom. Originally designed as an assistive technology for children with mild hearing loss, research over the past 20 years has shown that the benefits of sound-field amplification include improved academic achievement, speech recognition, attending skills, and learning behaviours (Rosenberg & Blake-Rahter, 1995). These authors provide an extensive review of the earlier literature.
Recent studies have consolidated the view that sound-field amplification technology enhances classroom learning. In 1999, Rosenberg et al. reported on a three-year project involving general education kindergarten, first and second grade classrooms. Their findings indicated that students in amplified classrooms demonstrated improvement in listening and learning behaviours, and progressed at a faster rate than their grade-alike peers in unamplified classrooms. Other recent study findings include the following: Long and Flexer (2001) cited a reduction in special education referrals by almost half for children in kindergarten through to fifth grade classrooms; Darai (2000) found that first grade students in classrooms with sound-field systems achieved greater literacy gains compared to control students; Flexer (2000) demonstrated improved reading test scores for first grade children, 85 per cent of whom were Native American; Flexer, Kemp Biley, Hinkley, Harkema and Holcomb (2002) noted a trend towards greater development of phonemic awareness skills for young preschool and kindergarten children. Benefits identified for teachers include reduced vocal strain and vocal fatigue, increased ease of teaching, increased versatility of instructional techniques, and increased teacher mobility (Rosenberg et al., 1999).
Few studies have investigated the efficacy of sound-field amplification in cross-cultural classrooms. Crandell (1996) found that the speech perception of 20 non-native English children with normal hearing sensitivity was significantly improved at speaker-listener distances of 12 and 24 feet. When reporting on the results of a three-month pilot project for a population of Inuit students living in a remote community in Northern Quebec, Eriks Brophy and Ayukawa (1999) showed significant improvements in speech intelligibility and attending behaviours with sound-field amplification.
Australian studies have shown that 50 to 80 per cent of Aboriginal and Torres Strait Islander children have sufficient middle-ear related hearing loss to adversely affect classroom performance (Nienhuys, 1994). The National Acoustic Laboratories (NAL), the research arm of Australian Hearing, developed a dual-channel sound-field amplification system incorporating features needed for use in remote Aboriginal communities, as well as for use in urban schools (Page, 1995). The numbers of sound-field amplification systems used in classrooms around Australia has been steadily increasing. The benefit of the dual-channel transmission system is that two teachers can use the system at the same time, or the second microphone can be handed around among the children during interactive class sessions (Page, 1995).
According to Flexer (2002), microphone techniques need to be demonstrated to teachers so they can learn strategies to utilise both single and dual channel transmission options more effectively. Teachers can speak more softly and with more varied vocal inflections because the sound-field system provides vocal projection. A keen advocate of sound-field amplification, Flexer (2002) noted that a pass-around microphone for students can 'enhance teacher effectiveness'. However, she concluded, teachers may need to use different teaching strategies to best take advantage of sound-field amplification technology.
A study on the effects of sound-field amplification intervention with Aboriginal and Torres Strait Islander children indicated that short and intermittent use of this technology produced changes in the dynamics of classroom communication (Massie, Theodoros, Byrne, McPherson & Smaldino, 1999). An additional finding was that using sound-field amplification facilitated increased classroom communicative interaction with peers (Massie, 2000). As noted in the literature, such interactions are their preferred way of learning (Howard, 1991; West, 1994).
Given that the classroom serves as a communication channel for learning, the question arose as to the effects any changes in communication may have on the learning capabilities of other children in mainstream cross-cultural classrooms. The aim of the present study was to examine the effects sound-field amplification had on the children's acquisition of specific educational goals, as routinely assessed within the school system.
This study differs from previous studies into the educational advantages of sound-field systems in that the majority of participants were ESL students. Additionally, a major component of the study design was to identify the patterns of use and range of additional benefits provided by single and dual-channel transmission options, which are reported in the companion article.
Twelve classes of Year 2 children participated in the project, the majority of whom were from non-English speaking backgrounds or of Aboriginal and Torres Strait Islander descent. Of the 242 subjects, 128 were male and 114 were female, with a mean age of 6 years, 8 months. Forty-three per cent of the children came from an ethnic background which was Vietnamese (23 per cent), Samoan (9 per cent), Spanish (4 per cent), or Aboriginal and Torres Strait Islander (7 per cent). A further 18 per cent were from varying ethnic backgrounds including Chinese, Greek, Italian and Fijian.
NAL Twin FM Sound-field Amplification Systems (Type 3032) were installed in each classroom. Each system features two lapel microphone/transmitters. As recommended by Flexer, Crandell and Smaldino (1995), the volume controls of the receiver/amplifiers were set to the highest level that allowed the teacher to more around the classroom without feedback ocsillation occurring. Four 8-ohm speakers were connected to the receiver/amplifier and mounted on the wall of each classroom. The loudspeakers were placed at ceiling height in the four corners of each room so they were angled towards the centre of the room (Flexer et al., 1995).
An information booklet was developed outlining the requirements of the project, the rationale behind sound-field amplification, and the benefits and use of sound-field technology. Prior to installation of the systems in each classroom, in-service training sessions were provided to each teacher, usually on a one-on-one basis. Training sessions addressed topics relating to classroom acoustics, speech perception difficulties, suggestions for management, and practical demonstration of the sound-field amplification systems.
Hearing screenings were performed on all the subjects at the beginning of the school year. The same tests were performed on a subset (25 per cent) of children mid-year and at the end of the year. The audiometer was a portable Oscilla SM950 Clinical Memory fitted with Silenta Super headphones to provide additional attenuation of background noise. Calibration of the audiometer was performed prior to each assessment visit. Thresholds at the frequencies 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz were averaged for left and right ears, and the average was related to hearing loss as categorised by Clark (1981).
Classroom acoustic measurements
Classroom acoustic measurements were carried out in each of the 12 classrooms. Using the protocols outlined by Smaldino and Crandell (1995, pp. 70-80), ambient noise levels, RT measurements, and teacher speech levels were recorded for each classroom. A Bruel and Kjaer sound level meter (Type 2235), set on the 'A' weighted scale and on slow response, was used to record the noise levels and teacher speech levels at five selected sites for each classroom. As the measurements were obtained during the warmer months of the year, ceiling fans were operational in each of the classrooms. Teachers were asked to read a standard passage at normal instructional intensity level both with and without the sound-field amplification system. Reverberation time measurements were recorded using a Goldline Reverberation Time Meter, model number GL60 (RT60), in conjunction with a pink-noise burst generator (model PN-3 A). Measurements were recorded in at the central point of each classroom and were measured at 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz.
Diagnostic net data
The Year 2 diagnostic net was used to evaluate educational outcomes. In 1995, the Queensland government initiated a process of early monitoring and assessment of children's development in literacy and numeracy. The process identifies children who need additional support. Teachers monitor each child's progress using key indicators of literacy and numeracy development. The indicators are grouped into phases which form a developmental continuum for each of reading, writing, and number skills. Teachers rate each child's progress in these areas at the end of Year 1, midway through Year 2, and at the end of Year 2. Teachers of children in Years 1 and 2 forward written reports to parents outlining the phase at which children are operating, a description of the phase, and comments on the children's progress in each area. For this study, we calculated the number of key indicators acquired by each child for each time interval i.e. from end of Year 1 to mid-Year 2, and from mid-Year 2 to end of Year 2. The number of indicators acquired within a time interval was used as the measure of educational advancement.
A within-subject crossover design was used, with each of the 12 participating classrooms acting as its own control (Kazdin, 1980). For classes 1 to 8, the two experimental conditions were unamplified 'OFF' and amplified 'ON'. Four of these eight classes began the school academic year in the amplified 'ON' listening condition, two classes having one microphone and two classes having two microphones. The other four classes remained in the traditional unamplified 'OFF' listening condition. Midway through the academic school year (at the end of Semester 1), the eight classes were crossed over to the other experimental listening condition. Classes 9 to 12 were alternated between the single-channel and dual-channel transmission options, each condition being for two terms (i.e. one semester) of the four-term school year. Ninety-two per cent of teachers used the amplification systems every day. Forty-two per cent of teachers used amplification for more than one hour but less than two hours each time, and 25 per cent of teachers reported using the systems for more than two hours each time.
The mean pure tone average hearing level for this population of children, calculated as the average of the thresholds at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, was 15.3 dB for the left ear and 14.9 dB for the right ear at the beginning of the year. These levels were at the upper limits of normal hearing as defined by Clark (1981). For the sample of children whose hearing levels were measured throughout the year, a repeated measures ANOVA, with frequency, ear and time as repeated measures and order as a between-groups factor, revealed a small but insignificant increase (3 dB) in average hearing loss with time. The results of a one-way analysis of variance (ANOVA), with class as a between-groups factor, performed on the hearing level at the beginning of the year indicated there was no significant difference in hearing levels between classes (p = 0.061).
Classroom acoustic measurements
Table 1 outlines the reverberation time measurements recorded for each classroom and the impact of the systems on the teacher voice levels received by the children. The effect of the systems on teacher voice levels across classrooms ranged from +4 dB to +10 dB with a mean of +6 dB. Mean ambient noise levels for occupied classrooms ranged from 64 dB to 72 dB, with a mean of 68 dB.
The Year 2 diagnostic net data were statistically examined with a view to investigating: a) whether use of the amplification system affected educational outcomes; b) whether some skills were more affected than others; c) whether family language affected outcomes; d) the effects of using single-channel and dual-channel transmission options.
Figures 1-3 detail the results for classes 1 to 8, which midway through the year switched between amplification 'ON' and amplification 'OFF'.
[FIGURES 1-3 OMITTED]
Figure 1 shows the number of skills acquired per semester for each of the three skill areas, with and without the amplification system. Beneficial effects of amplification were obtained in all three skill areas of reading, writing and numeracy. Averaged across the three areas, the number of skills acquired per semester increased from 4.1 without amplification to 5.8 with amplification. Although the absolute increase of 1.7 skills acquired was similar in each area, the effect of amplification relative to the number of skills acquired without amplification was particularly large for reading and writing.
The data were analysed with an ANOVA with order (system ON first/system ON second) as a between-groups factor. System (ON/OFF) and skill (reading, writing, number) were repeated measures factors. The main effect of system was highly significant (p<0.000001), and there was no significant interaction of skill with system (p>0.22).
The same ANOVA indicated a highly significant interaction between skill and order (with the system apparently being more effective when provided in the first semester). This finding, however, is a consequence of the study design. The experiment used was a crossover design so that each class acted as its own control. Suppose, for some reason, the skill increase during Semester 1 is normally greater than that during Semester 2, even when no amplification is involved. If amplification is used during Semester 1 (and withdrawn during Semester 2), then the inherently higher score for Semester 1 will inflate the apparent effects of the amplification system. Conversely, when amplification is used during Semester 2, the inherently lower score for Semester 2 will offset any advantages the amplification system may offer.
In this study, there did indeed appear to be a strong underlying advantage for Semester 1, at least for reading and writing, as shown in Figure 2. This differential is not related to amplification, as there were an equal number of classrooms with and without amplification during each semester. This was confirmed by two additional analyses.
[FIGURE 2 OMITTED]
To determine whether the amplification system had similar effects in each semester, we hypothesised that for each skill area the mean skill increase was the sum of the inherent (no amplifier) skill increase, plus the skill increase due to amplification (when it was present). Because we have mean skill increases observed under four conditions (amplification in Semester 1, amplification in Semester 2, no amplification in Semester 1, and no amplification in Semester 2), we can simply calculate the four underlying components of the score. These components are the no-amplification skill increases in each semester, and the separate effects of adding amplification in each semester. (That is, we did not assume that amplification had the same effect in each semester.) The results of this calculation are shown in Table 2. As can be seen, the amplification system produced broadly similar effects in each semester, especially when averaged across the three skill areas.
As a second check, we computed a semester correction factor equal to the Semester 1 score minus the Semester 2 score, averaged across all 12 classes. Half this difference was subtracted from all Semester 1 scores, and added to all Semester 2 scores. The resulting semester-corrected scores were subjected to the same ANOVA analysis, as previously described. The data correction had no effect on the average scores with and without amplification for each skill area (as shown in Figure 1). However, as expected, the effect of amplification did not now significantly depend on the semester in which it was used (p>0.1).
[FIGURE 1 OMITTED]
Figure 3 shows that the effect of amplification was similar across the subgroups of children differing in the language(s) used at home. The data were analysed with a three-way ANOVA with language as a between-groups factor, and amplification system and skill area as repeated measures factors. Language spoken did not interact significantly with either skill area or the effect of amplification.
[FIGURE 3 OMITTED]
Classes 9 to 12 used sound-field amplification throughout the school year. As previously discussed, the data were corrected to compensate for the increased acquisition of skills that occurred during the first time interval (holidays + Semester 1). The results are shown in Figure 4 (overleaf).
[FIGURE 4 OMITTED]
The data were analysed with a three-way ANOVA with order (one microphone first semester/two microphones first semester) as a between-groups factor. Skill area and number of microphones were repeated measures factors. There was no significant effect of number of microphones or interaction of number of microphones with order. The same ANOVA indicated a significant three-way interaction, with two microphones being better than one microphone for number skills for those classes which had two microphones first.
The House of Representatives Standing Committee on Education and Training recently published the findings of an inquiry into the education of boys (October, 2002). In this report the importance of developing strong foundation literacy and numeracy skills in the early years of schooling was emphasised. Given that the acquisition of educational outcomes for all school children is of national priority, the findings from this study have important ramifications. Beneficial effects of amplification were obtained in literacy and numeracy skills for Year 2 children in cross-cultural mainstream classrooms. For classes 1 to 8, the system effect per skill area per semester (1.7 skills for Semester 1 and 1.6 skills for Semester 2) was one-third of the total number of skills acquired in each semester. As skills are acquired with each passing semester, these results indicated that sound-field amplification intervention had a similar effect to increasing the length of each semester by an extra one-third.
The greater skill increase in Semester 1 than in Semester 2 observed in the study was probably accounted for by the times at which the teachers' assessment of the children's skills were performed. The Semester 1 increase was based on the change in scores between the assessment made at the end of Year 1 and the assessment made in the middle of Year 2, and thus included the six-week summer holiday break. The Semester 2 increase, from the middle of Year 2 to the end of Year 2, includes the much shorter winter holiday break. Presumably, the children continued to develop their skills, at least in reading and writing, during the holidays. There may, of course, be other factors contributing to the difference between semesters, also not related to amplification.
Classes 9 to 12 used single-channel or dual-channel amplification systems throughout the two semesters, the aim being to identify the patterns of use and range of additional benefits provided by the dual-transmission option. A major finding was that the number of microphones did not affect the rate of acquisition of educational outcomes. This was a surprising result, given that passing around a second microphone would facilitate peer exchanges, which, according to the literature, would enhance 'classroom talk' (Eriks Brophy & Crago, 1994) and hence provide a more culturally appropriate learning environment (Howard, 1991; West, 1994). Flexer (2002), alluded to the use of a pass-around microphone for students as a strategy that can 'greatly enhance teacher effectiveness'. Closer examination of the teacher questionnare data that formed part of the same study revealed that three of the four teachers in classes 9 to 12 used the second microphone every day for up to half an hour, with the remaining teacher using it every second day for up to an hour each time. All teachers reported the preferred activities for the second microphone to be the presentation of morning talks, e.g. sessions on 'news' or 'show and tell' sessions, as well as one-on-one presentations to the class, e.g. reading a book to the class. In view of the relatively small amount of time the second microphones were utilised during the course of the schoolday, it is not surprising that educational outcomes were not affected.
The mean number of skills acquired per semester for classes 9 to 12 was 4.85. This is intermediate to the mean values of classes 1 to 8 without the system (4.14 skills per semester) and with the system (5.82 skills per semester) (see Table 2). Comparisons between the two groups of classes (1 to 8 versus 9 to 12) are not as valid as within groups, however, as each class (and teacher) no longer acted as their own control. Either the value of 4.85 for classes 9 to 12 was lower than the system-on value of 5.85 for classes 1 to 8 because of this lack of adequate controls, or possibly the presence of the system for only hall the year in classes 1 to 8 created a halo effect. The latter may have caused the teachers to inflate the assessment of each child given by the teacher for the period in which the system was present and deflate the assessment for the period in which it was absent. Due to the extended duration of the experiment, and the fact that the assessments were a normal part of the teachers' reporting of each child's progress to parents, we don't think the creation of a halo effect was likely, though we did not rule it out.
A different phenomenon may have caused the impact of the sound-field systems to be underestimated in classrooms 1 to 8. It is possible that beneficial effects of the sound field systems installed in Semester 1 may have carried over to those classes in Semester 2, even after the system was removed. Such carryover effects were observed by Massie (2000), and they may arise if the enhanced acoustic environment provided by the system leads to positive communication behaviour patterns that persist after the system is removed.
Although not directly studied, teacher in-service training programs probably play a vital role in the effectiveness of sound-field amplification. As noted by Flexer (2002), problems can result when teachers place limitations on their teaching or when they teach in the same way with the technology as without it. A limitation of this study was that teachers received the same in-service training, but, due to constraints on their time, on an individual basis rather than as a group. The latter approach would have provided opportunity for discussion and expression of ideas. Regular group meetings may have proved beneficial as teachers became comfortable with using the equipment. Additionally, a greater emphasis on the demonstration of microphone techniques and strategies may have affected outcomes. Most importantly, teachers must be provided with ongoing support in order to feel confident in their knowledge of strategies for effective use of the equipment.
The results of this study highlight the listening difficulties faced by all school children--hearing levels that are less than optimal and noisy reverberant classrooms that do not promote the easy perception of speech. Although there was a worsening of hearing level over time of 3 dB, it was thought this difference was not of practical significance. Ambient noise levels, and RTs were extremely high, and confirmed there has been little change in classroom acoustic conditions from those reported in the literature over the past 20 years (Crandell & Smaldino, 2000). The majority of classrooms in this study were timber and exhibited minimal acoustic treatment (neither sound attenuation nor sound absorption). The majority had entire walls comprised of louvre windows and often were located along noisy timber corridors. The findings confirmed that there is an urgent need for consideration of the acoustic environment of classrooms to enhance the perception of speech.
The measurement of acoustic levels indicate that the sound-field systems improved the teacher's voice level by 6 dB on average. Although this is a very worthwhile improvement, it is only one aspect of the improvement in signal. Most children were closer to one of the loudspeakers than they were to the teacher. Consequently the system also increases the ratio of direct sound to reverberant sound. As reverberation decreases comprehension, the sound-field amplification system helps raise the speech above reverberation, as well as above noise.
This study supports the use of sound-field amplification to advance the acquisition of literacy and numeracy skills for children in mainstream classrooms, and not only for those children with identified hearing loss of with ESL backgrounds. At present in Australia, there are no enforceable standards for classroom acoustics. However, sound-field amplification may be viewed as a cost-effective part of the solution to improving classroom listening environments for all children.
cross cultural studies hearing acoustics communication problems comprehension outcomes of education
The authors would like to acknowledge Education Queensland and Brisbane Catholic Education for their support of this project. A sincere thankyou also to the Year 2 (2001) teachers and children from the following Brisbane schools for their cooperation: Dunwich State School; St. Francis Xavier Convent, Goodna; Goodna State School; Inala State School; St. Marks Convent, Inala: The Murri School, Acacia Ridge; St. Paul's Convent, Woodridge; West End State School; Woodridge State School. The statistical guidance provided by Lydia Storey (NAL, Sydney), and the technical support provided by John Cristaudo and Stan Brimson (Australian Hearing, Brisbane) are also gratefully acknowledged.
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Robyn Massie is a research scientist at the National Acoustic Laboratories of Australia, PO Box 237, Brisbane QLD 4001 Email: firstname.lastname@example.org
Harvey Dillon is the Director of Research at the National Acoustic Laboratories of Australia, PO Box 237, Brisbane QLD 4001
Correspondence concerning this article can be directed to Robyn Massie.
National Acoustic Laboratories
Table 1 Acoustic measurements for each classroom Teacher voice dB Teacher voice dB Voice level dB Class Mean RT system 'OFF' system 'ON' increase 1 1.8 63 71 8 2 1.0 65 71 6 3 1.9 68 72 4 4 1.6 69 74 5 5 1.7 69 74 5 6 1.9 67 73 6 7 1.5 67 73 6 8 1.3 63 73 10 9 1.2 67 72 5 10 1.2 66 70 4 11 1.5 62 70 8 12 1.4 62 69 7 Mean 1.5 66 72 6 Table 2 The first four rows show the skill increases observed, averaged across the four classrooms that experienced each of the conditions shown. The final two rows show the inferred effect of amplification in each semester. Reading Writing Number Average System OFF, Semester 1 3.25 3.19 7.44 4.63 System ON, Semester 1 5.53 4.49 9.02 6.35 System OFF, Semester 2 1.63 1.53 7.78 3.65 System ON, Semester 2 3.40 3.51 8.94 5.29 Amplification effect, Semester 1 2.28 1.29 1.58 1.72 Amplification effect, Semester 2 1.77 1.98 1.16 1.64
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|Publication:||Australian Journal of Education|
|Date:||Apr 1, 2006|
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