The purpose of this study was to investigate the effects of a peer-delivered "Corrective Mathematics" program ("CM"; Engelmann & Carnine, 1982) in a secondary general education classroom with students with low mathematics performance. Ten learners and 9 peer tutors participated in the study. Peer tutors instructed individuals or pairs of learners in the "CM" program for 10 weeks. Pre- and posttest data were collected on the learners and peer tutors using the Woodcock-Johnson--Revised Tests of Achievement (WJ--R ACH) Calculation and Applied Problems subtests. Results showed that students who were instructed by their peers with the "CM" program exhibited improved performance on both subtests of the WJ--R ACH. Specifically, the learners' average improvement on the Calculation and Applied Problems subtests of the WJ--R ACH were statistically significant. The performance of the peer tutors also improved on both subtests of the WJ--R ACH. The peer tutors' average improvement on the WJ--R ACH Applied Problems subtest was also statistically significant. Results are discussed in terms of the implications for effective mathematics instruction and the need for future research. (Contains 1 table.)