The present quantitative study evaluated the effects of Supplemental Educational Services (SES), a federally mandated component of No Child Left Behind, on student achievement in reading and mathematics. SES provides free tutoring outside of school to disadvantaged students who attend Title I schools in their third year of failing to achieve Adequate Yearly Progress on state assessments. In the present study, data from the fifth year of SES implementation in a large urban school were analyzed to determine if the mostly small and nonsignificant effects obtained in prior years were stronger as the tutoring services acquired additional refinement and maturity. A matched treatment-control group design was employed, in which students who received SES tutoring in reading, mathematics, or both were matched to similar schoolmates who were eligible for SES services but did not participate. Results showed consistently positive but small, nonsignificant effect sizes for the outcome measures. Student achievement results and its implication for policy and practice are discussed. (Contains 6 tables.)