Although response to intervention (RTI) has been widely discussed in education literature and is increasingly being implemented in schools throughout the U.S., few studies provide empirical evidence of improved school-wide student outcomes. Presented here are data and an effect size analysis of school-wide student reading gains in five elementary schools implementing RTI components and processes. One school that began the year with below norm skills generally closed the performance gap. Four schools began the year with above norm skills; three of these schools accumulated even greater advantage while one school's advantage diminished. Even as this study offers empirical data on the student outcomes in an RTI setting, more studies are needed before evidential and consequential validity claims can be made about RTI as a school improvement program. (Contains 9 tables.)