I don't know anything about the conversion etc but I just wanted to say I agree that Canadian schools (I was raised in Canada) are just run different than schools (especially ones in the deep south). It's not teach to the test as the one goal for the entire year, oh and lets not forget eyes forward, don't be different, act like sheep attitude;) <although that may be just where my kids all go to school currently>
Were those highly gifted classes you referenced as being Asian dominant where you are currently, or back in Canada? I would say they are probably only dominated in certain areas of Canada like that (Vancouver being one of them)I'm not sure that they would be truly "gifted" type schools though but more of high end, high academic type schools. Depending on the size of the community that your looking to return to, you would probably have many options that would be less of a pressure cooker etc (dual immersion schools etc)
Good luck with your decision. Welcome to the forum!