Since we moved to Toronto for grade 4, it did not affect us, gifted congregated starts in 4 but I have not heard of any child accomodated before that except one on the ABC Ontario board that got skipped.
Although they have been more accomodating, at least last year, for DD to log on during math and do her accelerated CTY which they didn't do in NYC. I am going to push for the same this year.