A 3-year study applied the four-dimensional pedagogical theory and model of transitional bilingual education in a school with a large Hispanic population, using mathematics content as the vehicle for teaching English. Subjects were approximately 200 fifth-grade limited-English-proficient (LEP) students in three cohorts in a 6-week voluntary summer program. Data on student achievement were drawn from Spanish and English math pre- and post-tests, with the students selecting the test language. The principal aims of the program were to improve LEP student achievement in math using both languages, and to prepare the students for middle school and help them maintain math skills during the summer. Results indicate overall mathematics improvement over the 3 years of the study, ranging from 3-27 percent gains in the four assessed areas of mathematics (fractions, charts and graphs, measurements and geometry, problem-solving); no negative differences or equivalent scores were noted. Overall score gains were 22 percent for the first cohort, 14 percent for the second, and 8 percent for the third. Annual gains differed for the four skill areas. In anecdotal reports, teachers reported more strengths than weaknesses in the program. Overall, the experiment was found successful. (MSE)