We have a spanish immersion program here that starts in kindergarten. The math and science scores are lower there than at the regular public school, but it's hard to know if it is due to the school curriculum or a selection bias (if kids who go there are not going to do as well in math/science anyway for other reasons).
I think it's a tough curriculum if you don't speak/read Spanish yourselves. In our district out in California, alot of bilingual kids go there, so if you are not bilingual yourself, your child will be at a disadvantage. HTH.
