Try not to worry too much - I think most parents who get a call from a teacher who's saying their child is really advanced would not mind a bit! It's wonderful that you are being proactive about this and doing something. Having read your options, all well-thought out, I agree that sticking with a great teacher who gets the student (you), is probably the best option for now. But if the parents start asking about possible acceleration, etc., I would be sure to discuss those options too, along with your reasons for leaning toward in-class differentiation.
I am glad that you aren't going to "let him be a helper" in a way that's different from what you have the rest of your students do. You have the right attitude about that as far as I'm concerned. And I think it would be entirely appropriate and helpful to get it across to the other teachers to comment just what you said here: "ALL students are expected to help their peers in my classroom, but not as a semi-permanent differentiation strategy." Well, maybe you could say "but I would use a differentiation strategy for this student" to show that having a kid be a helper isn't a differentiation strategy... (Really, I wouldn't want you to say anything that would irritate other teachers, but it would be nice if other teachers got that this doesn't work in itself as differentiation.)
Good luck! And thanks for being such a caring teacher.
