Earning a college degree is widely recognized as the most reliable pathway to economic stability (Carnevale, Smith, & Strohl, 2013). But it is known from a wide range of research that access to college is neither easy nor equitable, and that traditionally underrepresented students (including low-income students and Black and Latino students) continue to matriculate and earn degrees at disproportionately low rates (Bailey & Dynarski, 2011; Black & Coca, 2017; Kane, 2004). Also known is that the solution to these challenges cannot be found solely in the classroom (Heckman & Rubinstein, 2001; Heckman et al., 2006). Indeed, there is a growing consensus that college success relies on a concert of academic and social emotional learning (SEL) skills (Farkas, 2003; Farrington et al., 2012; Durlak, et al., 2011), strong guidance during the college application process (Roderick et al., 2008; La Rosa et al., 2006), and financial, academic, and social support throughout college (Kuh et al., 2006). What is less clear is the specific types of programming that can effectively close the opportunity gaps. Mentoring programs represent one promising area, with a large body of research showing that relationships between adults and youth, such as those formed in mentoring programs, can improve youth's odds of success. The iMentor College Ready Program combines school-based mentoring with technology and aspects of whole school reform in an effort to boost students' college readiness. The program matches low-income youth with college-educated mentors and focuses on helping them develop close relationships through online communication and monthly in-person events, held over the course of students' four years of high school. In 2010, the Social Innovation Fund (SIF) awarded a grant to iMentor to support a rigorous evaluation of the College Ready Program. iMentor engaged the Research Alliance for New York City Schools to conduct a mixed methods evaluation of the program in eight New York City high schools. The study included about 1,600 students who received iMentor programming and comparison students who did not have access to iMentor. This evaluation assessed the implementation of iMentor in the eight study schools and its impact on students' social and emotional learning, academic outcomes (like attendance and progress toward high school graduation), college going activities, and transitions to college. This is the final report of the iMentor study. It summarizes the findings about the College Ready Program's implementation and examine its effects on key student outcomes. It focuses particularly on students' 12th-grade outcomes in order to assess the program's cumulative impact over four years. In exploratory analyses, it considers whether students who participated more fully or felt closer to their mentor experienced larger impacts from the College Ready Program. The report concludes with some implications of this study for both iMentor and the field at large. [For the technical appendices, see ED609340. For the previous report of the study, "iMentor's College Ready Program: Examining Implementation and Impacts for 10th Graders," see ED591554.]