Research on second language learning suggests that age or age-related factors are a major variable in the acquisition of a second language for school. In the early stages of acquisition, older students are faster and more efficient learners, with the advantage of more advanced cognitive development in the first language. This early advantage diminishes after the first year of second language learning for adults, but remains for older children and adolescents. Adolescents past puberty are likely to retain an accent but are capable of developing complete second language proficiency. When schooled only in the second language, students in the 8-to-12-year range on arrival may be the most advantaged learners of school skills in the second language. Older students have less time to make up lost years of academic instruction easily. The effect of age diminishes over time as the learner becomes more proficient in the second language. Differences are generally found through the first five years after arrival. It takes language minority students in any type of program a minimum of four years to reach native speakers' level of school language proficiency and may take eight or more years, depending on a variety of factors. (MSE)