And guess what...? Yep, it's working.
In 1998 voters passed Prop 227 which practically banned schools from teaching students reading, writing and mathematics in their native language first. San Francisco, always one to go against the status quo, found a way around the mandate and now, around 30% of the English-learning students are enrolled in bi-lingual education programs.
Read the article in sfgate.com that outlines the results from the recent Stanford analysis: http://www.sfgate.com/education/article/S-F-seen-as-model-in-bilingual-education-over-5229826.php