THIS RESEARCH examines the effectiveness of Peer-Assisted Learning Strategies for First-Grade Readers (First-Grade PALS) as a tool for enhancing the reading achievement of different learner types, particularly low-achieving students, representing the range of academic diversity typically present in primary grade classrooms. First-Grade PALS helps teachers to accommodate this diversity (a) by decentering instruction through peer mediation so that students become more actively involved in the learning process, (b) by including provisions for integrating phonological and alphabetic skills into the decoding of words in connected text, and (c) by providing extensive and repeated exposure to a variety of children's literature. In this research, the efficacy and feasibility of First-Grade PALS were examined in naturally constituted, academically heterogeneous first-grade classes, during rime normally allocated for reading instruction. Twenty first-grade teachers and 96 first-grade students (46 low, 20 average-, and 20 high-achieving) participated. Ten teachers incorporated First-Grade PALS into their reading program; 10 continued to teach reading as usual. Data collected included (a) time-series phonological awareness and reading fluency data and (b) pre-and post-measures of concepts of print, decoding, fluency, and comprehension. Students and teachers also were asked to rate their satisfaction with various aspects of First-Grade PALS. Results indicate that all learner types were positively affected by participation in First-Grade PALS, with the greatest gains indicated for low-achieving students. Likewise, both students and teachers implemented First-Grade PALS with relative ease, demonstrated high fidelity, and reported high levels of satisfaction.