This study examined the effects of a peer-delivered Corrective Mathematics program on math ability of low-performers in a secondary general education classroom. The Calculation and Applied Problems subtests of the Woodcock Johnson Achievement Test were used to assess math ability following intervention. Both learners and tutors showed statistically significant increases in scores on the Applied Problems subtest; the learners showed significant increases in scores on the Calculation subtest. (Copyright © 2011, National Institute for Direct Instruction (NIFDI). All rights reserved).