This chapter describes how a well-respected peer-led academic support model, Supplemental Instruction (SI), has been successful in improving grades and reducing failure in high-risk courses at LaGuardia Community College since 1993. Supplemental Instruction at a Community College: The Four Pillars Joyce Ship Zaritsky, Andi Toce Supplemental Instruction (SI) is a recognized and highly respected academ- ic support program available worldwide in institutions of higher learning (Martin and Arendale, 1990; Martin, Arendale, and Associates, 1992; Ogden and others, 2003). Outcomes have demonstrated that SI can contribute to significant change in students' performance by raising grades and reducing failure in high-risk courses. SI was first piloted at LaGuardia Community College in 1993 with three courses. By 2002-03 the program had expanded to target and support one hundred courses (Zaritsky 1994, 1998, 2001). There have been 136 participating instructors and 234 SI leaders in LaGuardia's SI program since its inception. This indicates that of the 234 leaders in the program's history, 184 are former leaders, and 50 are current leaders. Data collected during this time show that students who attend SI sessions achieve, on average, one letter grade higher than those who do not attend. (See Table 3.1.) The data also show that students who participate in SI are less likely to drop the targeted course and therefore more hkely to persist. Over the years since program inception, we have also learned that running a successful SI program on our campus depends on the support of four interdependent groups, or pillars: SI supervisors, SI leaders, faculty, and administration. ®WILEY ItiterScience* D I S C O V E H J O M E I H I N G G R E A I - \ - 5 NEW DIRECTIONS FOR TEACHING AND LEARNING, no. 106, Summer 2006 © Wiley Periodicals, Inc. Published online in Wiley InterScience (viTvw.interscience.wiley.com) • DOl: 10.1002/tl.230