This report was prepared for the National Center for Education Evaluation and Regional Assistance, Institute of Education Sciences, under contract ED-06C0-0029 with Regional Educational Laboratory Mid-Atlantic administered by Pennsylvania State University. IES evaluation reports present objective information on the conditions of implementation and impacts of the programs being evaluated. IES evaluation reports do not include conclusions or recommendations or views with regard to actions policymakers or practitioners should take in light of the findings in the report. This report is in the public domain. Authorization to reproduce it in whole or in part is granted. While permission to reprint this publication is not necessary, the citation should read: Wijekumar, K., Hitchcock, J., Turner, H., Lei, PW., and Peck, K. (2009). A Multisite Cluster Randomized Trial of the Effects of CompassLearning Odyssey® Math on the Math Achievement of Selected Grade 4 Students in the Mid-Atlantic Region (NCEE 2009-4068). Washington, DC: National Center for Education Evaluation and Regional Assistance, Institute of Education Sciences, U.S. Department of Education. This report is available on the Institute of Education Sciences website at http://ncee.ed.gov and the Regional Educational Laboratory Program website at http://edlabs.ed.gov.