The large number of limited English proficient (LEP) children in U.S. schools and the uncertainty about the impact of bilingual education versus English immersion on their achievement warrant rigorous investigation of the effects of "English immersion laws." We estimated the impact of "Question 2", the Massachusetts English immersion law, and explored whether programs provided to LEP students before and after "Question 2" imparted different language and reading skills. The results suggested that "Question 2" had no substantial effect on third-grade LEP students' reading achievement; there was suggestive evidence that pre- and post-"Question 2" programs might attach emphasis to different subskills. (Contains 5 tables and 3 figures.)