The Expository Reading and Writing Course (ERWC) was developed by California State University (CSU) faculty and high school educators to improve the academic literacy of high school seniors, thereby reducing the need for students to enroll in remedial English courses upon entering college. This report, produced by Innovation Studies at WestEd, presents the findings of an independent evaluation of the ERWC funded by an Investing in Innovation (i3) development grant from the U.S. Department of Education. The study sample for the evaluation included more than 5,000 12th grade students in 24 high schools across nine California school districts in the 2013/14 school year. The authors of the report found that the ERWC has a statistically significant positive impact on student achievement. Results from an analysis of implementation fidelity are also presented, along with qualitative findings based on survey data from study participants. Appendixes include: (1) Statistical Power for Impact Estimates; (2) Data Collection Instruments to Measure Fidelity of Implementation; and (3) Rubric for Calculating Fidelity of Implementation for Each Component of the Expository Reading and Writing Course.