I would try not to worry about it too much at this point - since you're both new to the school, let your daughter give the class a try and see how it goes. As spaghetti mentioned, there are many different flavors of Montessori as well as many different degrees of willingness to differentiate in any given classroom. Because Montessori in general tends to be less class-wide everything's the same, there's a good chance your dd's new teacher will have time to spend with her and observe and she may change her mind re acceleration before the quarter's over - or she may decide she can work with dd and differentiate in class. Meanwhile if your dd complains of boredom/etc.. you can meet with the teacher, see what her impressions are, and possibly broach the subject again, this time sharing her IQ scores.
The other thing I'd recommend doing is getting to know other parents at the school - you can learn a lot about how a school operates by talking with parents who've been there a few years. Having that type of knowledge in your back pocket can be very helpful when advocating.
Best wishes,
polarbear
