This study compared the academic performance of youth at varying levels of child protection system (CPS) involvement to understand whether a CPS achievement gap existed, and if so, whether more extensive involvement in CPS was associated with poorer academic performance. Standardized test scores of math and reading were compared for youth in the general population (who had no CPS involvement; n=410,491), youth with CPS involvement but no out-of-home placement (n=6,875), and youth with CPS involvement that led to an out-of-home placement (n=2,122). Significant evidence of an achievement gap for youth involved in CPS existed, even after controlling for socioeconomic status and race. More extensive CPS involvement appeared to be associated with significantly poorer performance but this difference disappeared when controlling for socioeconomic status and race. Findings suggest a need for policies that support collaboration, training and information sharing between CPS and school systems as well as specific CPS assessment and intervention strategies. The troubling consequences of the achievement gap provides a dire warning to the people and institutions charged with the care and education of youth in CPS. The CPS achievement gap identified in this study is an additional barrier that these vulnerable youth must overcome as they transition to adulthood.