Several limitations of this review can be identified. One such limitation is the noted lack of single subject studies included in the analysis. Much of the previous work in classrooms examining behavior management techniques was conducted using single subject methodology. This body of research provides important information about the functional relation between various classroom management practices and student behavior. However, given the concerns with current methods to analyze single subject data to calculate an effect size, the authors consciously chose not to include these studies. The consequence of excluding single subject studies means the effect sizes of universal classroom management obtained in this study may be biased. However, obtaining effect sizes from single subject studies that are not comparable to classroom effect sizes based on group studies was determined to not offer additional information to this study. Another limitation is that studies in which classroom management was examined but that did not include a measure of student behavior were not included in this review. A meta-analysis with both academic and behavioral outcomes would be the ideal, however given the paucity of group studies in this area, it was not possible. Finally, due to the small sample of effect sizes a general lack of power affected the ability to do moderator analyses. Future research should address these issues.