The purpose of this study was to examine the Students Who Achieve Together (SWAT) peer tutoring program at Greystone High School (an Illinois suburban high school of approximately 1500 students), and to use the information gathered to evaluate the program's effectiveness and provide an analysis for future decision-making about the program. In order to accomplish the purpose, the following research questions guided this study: 1. To what extent, if any, did the SWAT program affect the participating tutees' grades in the tutored class? 2. What is the perceived effectiveness of the SWAT program by the tutees, tutors, teachers, and school administration? 3. What barriers prevent students who are eligible for the SWAT peer tutoring program from participating? This mixed method program evaluation study investigated the effectiveness of the SWAT program by analyzing archived data, collecting survey data, and conducting interviews and focus groups. Tutors, tutees, teachers, and administrators who directly experienced or supported SWAT between the 2014-2017 school years (and were still in attendance) were invited to participate in the study. The study concluded that SWAT was effective at improving the grades as measured by grade growth of tutees in the tutored course. Additionally, this study confirmed the significant positive effect of peer tutoring as previously noted by other published research. Furthermore, tutors, tutees, teachers, and adult stakeholders generally perceived SWAT to be an effective tutoring program because of the common classroom experience, the safe tutoring environment, and the connections associated with a peer relationship. In addition to the study's focus on the program's effectiveness, the study identified barriers that might limit the use of SWAT. The study found that 1) negative social stigma associated with peer tutoring and 2) the time that SWAT peer tutoring was offered (lunch hours) were perceived barriers that might limit student participation. Additionally, this program evaluation identified four recommendations that SWAT should consider implementing in the future to improve its effectiveness. Moreover, by studying the program at Greystone High School and evaluating its effectiveness, this study 1) advanced the research on out-of-class peer tutoring model at the high school level to support all general education students, and 2) presented general recommendations for high school peer tutoring programs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]