In 2012, WestEd received a "Development" grant from the U.S. Department of Education's Investing in Innovation (i3) competition to develop and implement Internet-based Reading Apprenticeship Improving Science Education ("iRAISE"). "iRAISE" was implemented in Michigan and Pennsylvania and was provided to over 100 teachers who served approximately 20,000 students during the grant period. This report presents findings from the randomized control trial of "iRAISE," which took place during the 2014-15 school year and investigated the impact of the program on teacher and student outcomes. Data sources for this report include teacher surveys; PD observations and attendance records; school district student records; and an assessment of students' literacy skills. Despite levels of implementation that did not meet the expectations of the program developers, teachers self-reported that they did change their classroom practice as a result of the "iRAISE" program, and impacts of "iRAISE" were greater for students who were performing at lower levels of incoming achievement. Given that "iRAISE" had an impact on teacher practices in literacy instruction and increased benefits for low-achieving students-consistent with positive findings from prior studies, evaluators express confidence in the promise of low-cost, accessible, and high-quality online-only professional Development (PD), addressing the needs of schools struggling to meet the demands of literacy for college and career readiness. Appended are the following: (1) Considerations for Statistical Power; (2) Details of the Approach to Estimating Impacts; (3) Reporting the Results; (4) A Post-Experimental Method to Assessing Impact under Strong Implementation; (5) Fidelity of Implementation; and (6) Teacher Survey Constructs.