According to the National Assessment of Educational Progress (NAEP), just over 70 percent of students nationally arrive in high school with reading skills that are below "proficient"--defined as demonstrating competency over challenging subject matter. Of these students, nearly half do not exhibit even partial mastery of the knowledge and skills that are fundamental to proficient work at grade level. These limitations in literacy skills are a major source of course failure, high school dropout, and poor performance in postsecondary education. While research is beginning to emerge about the special needs of striving adolescent readers, very little is known about effective interventions aimed at addressing these needs. To help fill this gap and to provide evidence-based guidance to practitioners, the U.S. Department of Education initiated the Enhanced Reading Opportunities (ERO) study--a demonstration and rigorous evaluation of supplemental literacy programs targeted to ninth-grade students whose reading skills are at least two years below grade level. As part of this demonstration, 34 high schools from 10 school districts implemented one of two reading interventions: Reading Apprenticeship Academic Literacy (RAAL), designed by WestEd, and Xtreme Reading, designed by the University of Kansas Center for Research on Learning. These programs were implemented in the study schools for two school years. The U.S. Department of Education's (ED) Office of Elementary and Secondary Education (OESE) funded the implementation of these programs, and its Institute of Education Sciences (IES) was responsible for oversight of the evaluation. MDRC--a nonprofit, nonpartisan education and social policy research organization--conducted the evaluation in partnership with the American Institutes for Research (AIR) and Survey Research Management (SRM). The goal of the reading interventions--which consist of a year-long course that replaces a ninth-grade elective class--is to help striving adolescent readers develop the strategies and routines used by proficient readers, thereby improving their reading skills and ultimately, their academic performance in high school. The first two reports for the study evaluated the programs' impact on the two most proximal outcomes targeted by the interventions--students' reading skills and their reading behaviors at the end of ninth grade. This report--which is the final of three reports for this evaluation--examines the impact of the ERO programs on the more general outcomes that the programs hope to affect--students' academic performance in high school (grade point average [GPA], credit accumulation, and state test scores) as well as students' behavioral outcomes (attendance and disciplinary infractions). These academic and behavioral outcomes are examined during the year in which they were enrolled in the ERO programs (ninth grade), as well as the following school year (tenth grade for most students). Appendices include: (1) The ERO Programs and the ERO Teachers; (2) ERO Student Survey Measures; (3) ERO Implementation Fidelity; (4) State Tests Included in the ERO Study; (5) Response Analysis and Baseline Comparison Tables; (6) Technical Notes for Impact Findings; (7) Statistical Power and Minimum Detectable Effect Size; (8) Supplementary Impact Findings; (9) Baseline and Impact Findings, by Cohort; (10) The Association Between Reading Outcomes and Academic Performance in High School; (11) Variation in Impacts Across Sites and Cohorts; (12) Program Costs; and (13) Poststudy Adolescent Literacy Programming in the ERO Schools: Methodology and Additional Findings. (Contains 97 tables, 23 figures, 2 boxes, and 185 footnotes.) [This paper was written with Edmond Wong. For the first-year report, see ED499778. For the second report, see ED503380.]