Out-of-school programs provide a context for enriching academic experiences. This study describes a 12-week after-school reading program, Project Expanding Horizons, which is based on the Schoolwide Enrichment Model-Reading (SEM-R) framework. SEM-R has three phases: exposure, supported independent reading, and choice. The exposure phase is designed to broaden students' literature experiences through short read-alouds. During the next phase, supported independent reading, teachers circulate and hold conferences with students as they read independently from self-selected books. Teachers give guidance to students in selecting books of appropriate challenge during this phase and promote thinking about reading through questioning and discussion. Finally, during the last stage, teachers give students a choice of a variety of activities related to their reading. The program provided wide exposure to books and emphasized individually challenging reading, including a specific focus on meeting the needs of advanced readers. In this study, the participants included 155 students in grades 3-6 from 3 demographically diverse districts. Average weekly gain scores in reading fluency were compared to grade-level national norms. Third and fifth graders showed statistically significantly higher gain scores than the national sample; fourth and sixth graders did not. These results suggest that participation in the after-school program may have contributed additional support to students' growth in reading achievement over the course of 12 weeks. Further analyses indicated similar gain scores across subgroups by gender, district, and entry reading level. Thus, this program shows potential benefits for both low-ability and high-ability readers. (Contains 6 tables.)