Neurotik’s post says just about everything I was about to say, speaking as the child of a Special Education teacher. The NY State Billingual Education program, over the years, doesn’t appear to be all that much different from the others I have observed, and it… really doesn’t work all that well, based on ancedotal, but strong evidence of opinion, from the community of teachers that she is a part of.
By which I mean, everyone agrees that it’s… not a good idea.
On the other hand, immersion tends to disrupt the flow of the normal classes, leading into the ghettoized billingual education you have now. For the amount of care we put into the design of our school system, it’s a bit of Hobson’s choice, we’re not going to get good results either way.