A study assessed the effectiveness of the Success for All Program for grade-one English-as-a-Second-Language (ESL) learners in bilingual or ESL programs in three California elementary schools. The reading instruction program provides both native (in this case, Spanish) language support as well as English language instruction and materials. The three schools in question were matched with comparison schools in their districts, that were similar in level of student disadvantage and other factors. The 2-year evaluation measured student (n=313) progress from kindergarten entry (receptive vocabulary) to the end of first grade (phonetic synthesis skills, recognition of common sight words, and text comprehension). Analysis of the results indicates that the 2 years of instruction in the Success for All program were effective for both students taught in Spanish-English bilingual programs and in ESL programs. While the instruction raised the average student performance, it also raised the performance of the lowest-performing students, with some of the largest treatment effects occurring in this group. A suggested area for further research is the monitoring of achievement over time. (MSE)