We found with our MG DS this year in K that Immersion was the key to making K work. For example in math he knew all of the material but he got to learn something during math still, because he learned the Spanish vocabulary.
We speak Spanish at home too, but the level he was learning at school was much deeper.
I would be careful to give up immersion for the promise of something deeper in a regular classroom. I don't know your school, but generally meaningful differentiation is *HARD* even when the teacher is committed. And year after year the success of it will depend on each new teacher.
Good luck!
