This study examined the impact of the Lighthouse program, a school-based, after-school remediation program in the Chicago Public Schools, on student academic achievement. The Lighthouse program included an extra hour of instructional time and an hour of recreational time. Between the two activities, students received a healthy late afternoon meal. Study data came from 2001 surveys of principals, teachers, and students at 491 elementary schools and from student test scores. Results indicated that between 2000 and 2001, Lighthouse students made 1-month gains in reading and math over non-Lighthouse students. Lighthouse students in predominantly African American schools were performing better in reading than their counterparts in schools that were not predominantly African American. Lighthouse students in high-poverty schools were doing much better than their counterparts in schools without high poverty percentages. Lighthouse students in high-poverty schools were least likely to be taught by their regular school day teachers, whereas, in predominantly minority schools, Lighthouse students were likely to have the same teacher from the regular school day. Predominantly African American and low-normed schools were more likely to extend the school day and/or serve more students. (Contains 29 references.) (SM)