Just five years after California voters approved Proposition 227, which replaced bilingual education with English-only programs for most California LEP students, the number of English learners who scored "proficient' on the state's language test has risen significantly. Such scores among youngsters enrolled in English-only programs rose from 9 to 30 percent between 2001 and 2002, while students who remained in bilingual programs (because their parents sought a waiver from the new regulations) went from 3 to 16 percent proficient.
"English-only students do better on state test," by Nanette Asimov, San Francisco Chronicle, March 26, 2003