This paper examines the outcomes and descriptions of the existing studies on K-12 online learning effectiveness and provides a literature review. There are a number of rigorous studies that have examined the question, "Is online learning effective?" However, there is not a single, large-scale, national study comparing students taking online courses with traditional students, using control groups in the instructional design. The most in-depth, large-scale study to date is a meta-analysis and review of online learning studies from the U.S. Department of Education. This paper contains three sections: (1) a summary of the major study by the U.S. Department of Education, (2) a brief literature review of online learning research and studies, and (3) future research recommendations. The conclusion of the meta-analysis of these studies is that online learning offers promising, new models of education that are effective.