Due to a lack of power, the homogeneity in the sample of effects sizes indicated no moderator variables could account for differences between studies. It is not possible to determine which treatment components contributed to the overall effects due to the small sample of studies included in the review. A leaner package such as GBG may be as effective as a more comprehensive package such as COMP. Without adequate treatment fidelity data, it is difficult to determine what level of fidelity is necessary to establish effective universal classroom management. Although fidelity data could not be analyzed in the current synthesis, one study did report outcomes based on level of implementation. The classroom level effect size in Gottfredson et al. (1993) calculated for all levels of implementation was -.04 (ICC=.05) and -.03 (ICC=.10). However, when only high implementation classrooms were analyzed, the classroom level effect size increased to .54 (ICC=.05) and .38 (ICC=.10). This disparity in classroom level effect sizes indicates the importance treatment fidelity may play in the magnitude of outcomes.