My daughter (4 yrs 10 months) is bilingual (Japanese,English) and will be starting kindergarten next year. We currently live in the U.S.; her English is capable, but still fragmented and below her peers' level.
I have my eye on a French immersion school because their educational ratings are well above other schools in the area. My wife is still ambivalent about what school to choose, so she was talking with my daughter's preschool teacher about it, and the teacher recommended a standard school that has better than average educational ratings.
The preschool teacher's thinking is that because my daughter's English level is lacking, a standard school would help her catch up in her language skills and that an immersion school might slow her down. My thinking was that at an immersion school, everybody would be starting from the same level, so her English would be less of a hindrance in learning, and as an extension, it would also be less imperative for her to reach the level of her peers - she could learn at her own pace.