Cognitive behavior modification (CBM) has been used for the past 25 years to mitigate maladaptive behaviors through the use of covert self-statements. Yet few reviewers have examined the use of CBM in school settings to reduce hyperactive-impulsive and aggressive behaviors in children and youth. This meta-analysis examined the outcomes of 23 studies. The mean effect size across all the studies was 0.74, and 89% of the studies had treatment participants who experienced greater gains than their control counterparts on posttest and maintenance measures when exposed to a treatment with a cognitive component. These results are discussed in terms of study characteristics and design, and recommendations for future research are made.