Classwide peer tutoring (CWPT) involves the whole class in reciprocal roles of tutor and tutee. It has demonstrated effectiveness in regular and special education, across elementary, secondary and college settings (Greenwood et al., 1991). Yet to date there is only one study that has assessed its efficacy in physical education (Johnson & Ward, 2002). The purpose of this study was to examine the effects of CWPT on the performance of sixth-grade middle school students in a volleyball unit. Physical education (PE) was taught daily for 48 minutes. This study was conducted over 20 lessons. Participants were four average and low skilled students (2 males, 2 females) selected from a class of 21 students. An A-B-A-B single subject withdrawal design was employed to examine the effects of CWPT on (a) number of total and correct trials of volleyball tasks, (b) student's acceptability of the intervention, and (b) PE professional's acceptability of the intervention. The volleyball tasks were presented on task cards and included one or two stated criteria for performance. Data for total and correct trials are reported as number of trials divided by the duration of the practice session of each lesson (rate per minute). The students, the teachers and a group of PE professionals evaluated the social validity of the intervention and its results. Interobserver agreement was conducted on 36% of the observations with a mean of 97% agreement. Results indicate that total trials increased during the intervention for three of the four participants. The means of total trials ranged between 11-16 in baseline and between 21-27 in the interventions. Student's correct performance also increased during the intervention although correct performance was often variable. The means of correct trials ranged between 4-9 in baseline and between 11-18 in the interventions. The social validity data show that CWPT is an acceptable pedagogy to use in PE classes. This study extends the literature by (a) supporting CWPT as an effective instructional strategy by demonstrating its effects on student engagement in an ecologically valid setting; (b) extending the generality of CWPT to middle school PE, and (c) by reporting on the social validity of CWPT in PE by the students, their teachers, and by a panel of PE professionals. Future research should examine how best to train students, simplify or eliminate the use of task cards as part of the instruction, and emphasize students' accountability as part of the CWPT strategy. Keyword(s): middle school issues, performance, professional development