During the summer months, most of the students with Limited English Proficiency (LEP) are at great risk of falling further behind in reading and mathematics due to lack of exposure to the spoken and written English language in their homes. The purpose of this study was to examine the short-term effects of a summer program on the literacy and mathematical development of LEP students in a K-12 urban school setting. A mixed method descriptive design using pre and posttest measures was utilized. The quantitative component included the use of (a) descriptive statistics and (b) two-related-samples nonparametric test (Wilcoxon signed-rank test). The assessment instruments that measured students' knowledge in reading and math was administered before and after participation in the summer program. The qualitative component consisted of a focus group conducted with the program teachers. The summer program LEP participants demonstrated an overall statistically significant increase in all reading and mathematics assessment scores from pretest to posttest. The program appears to be working most effectively for students with the least amount of reading and math skills, as measured by scores on pretest. Moreover, teachers' positive feedback regarding progress on the socialization skills necessary for success in the classroom makes the program critically supportive for this at-risk population. Educators need to increase their knowledge of the effects of instructional summer programs on the language acquisition of LEP students in order to improve the students' academic development. (Contains 9 tables and 7 figures.)