Joanne has an interesting post on the topic here.
I discussed bilingual education before, here:
Second: The Teacher/Students
Third: Progressive Education
Fourth: Horrible Is Great
Fifth: Not Politically Correct
Sixth: The Final Class Begins
Those posts come from my experiences at Sac State getting my Cross-cultural, Language, and Academic Development certification. (No, I don't fully understand the the title, either.)
An interesting development is that I currently have as a student a relative of the professor in story #5 above.
And here's a little information on research into bilingual education.