Nationally, two-thirds of high school students are unable to read and comprehend complex academic materials, think critically about texts, and synthesize information from multiple sources, or communicate what they have learned. Without a substantial change in their academic literacy, U.S. high school students face continued academic problems in high school and college because they are unable to handle the quantity and complexity of assigned reading (ACT, 2012). The Reading Apprenticeship instructional framework was developed two decades ago to help teachers provide the literacy support students need to be successful readers in the content areas. It has since reached over 100,000 teachers in schools across the country, at the middle school, high school and college levels. In 2010, the program developers received a "Validation" grant from the Department of Education's Investing in Innovation Fund (i3) competition to scale-up and conduct a randomized controlled trial of the intervention through a project called Reading Apprenticeship Improving Secondary Success (RAISE). This study explored implementation questions as well as mediating impact and longer-term impact on student achievement. Questions included: (1) To what extent is RAISE implemented in a way that is consistent with the program model and underlying theory of action?; (2) What are the effects of RAISE on teacher practices and teacher attitudes?; (3) What are the effects of implementing RAISE on student engagement, and reading attitudes and behaviors?; and (4) What are the effects of implementing RAISE on student literacy achievement? The study took place in 42 high schools in California and Pennsylvania. Professional development was provided to teachers in a central location within each state. Teachers were offered on-site support through monthly meetings led by teacher leaders. The primary sources of data collected and presented in this paper are student record data collected from the district, monthly teacher surveys collected over three years (27 total), student surveys collected at the end of each implementation year and an on-line student literacy assessment developed and collected by the Educational Testing Service (ETS) at the end of each implementation year. Findings from this study demonstrate the success of the RAISE project in providing teachers with training and support at scale to help them change their instructional practices in order to foster metacognitive inquiry and support comprehension, particularly in science. These findings are consistent with positive findings from other studies of Reading Apprenticeship. The primarily positive, yet not statistically significant results for the full sample indicate that the study's sample size may not have been large enough to detect a modest size impact. The results from this study point to several areas in need of further investigation. Specifically, the differences in impact by subject area and state need to be better understood. 5 exhibits are appended.