School practitioners working from an evidence-based practice framework are expected to implement interventions that are effective with students. In the current study, the authors explore the feasibility of that expectation in light of the availability of critical effect size information necessary for making informed intervention decisions. Effect sizes for 51 school-based programs endorsed as effective by authoritative sources were reviewed. Effect size analyses reveal that the programs were not, on average, highly effective. Difficulties finding effect size information and programs with high effect sizes are discussed. Recent advances in evidence-based programs and suggestions for increasing the feasibility of evidence-based programs in schools are offered.