This study employed group randomized trials to investigate the effects of self- and peer-monitoring on the academic vocabulary and content knowledge of students with learning disabilities and low achieving students in social studies. Fourth grade students were randomly assigned to either treatment or control groups on a class level. Results indicated that there was a significant interaction effect between the intervention and students' pretest scores on academic vocabulary acquisition; the intervention was more effective for students with lower scores in the pretest than those with higher scores. In addition, there was a significant intervention effect on content knowledge acquisition; the effect size of the growth of the treatment group on the content knowledge test was significantly larger than that of the comparison group. Teacher interviews also revealed that teachers viewed the intervention positively. Implications for practice and suggestions for future research are discussed.