This report from the Civil Rights Project and Jacinta Ma summarizes major research on trends in ELL education including how long it takes for ELL students to learn English; the best types of language support programs; results of Proposition 227 in California; the legality of one-year language programs; and how ELL students are assessed.
Ma, J. (2002, September). What works for the children? What we know and don't know about bilingual education. Cambridge, MA: The Civil Rights Project Harvard University.