Honestly, I think you should find out exactly what test they plan on using. The more knowledgable you are, the better you understand things and also can determine if something is right or not. Just because a school tests a child doesn't mean the tester is necessarily good at testing a gifted child. Most of the time (I think I read 85%) when a parent suspects a child is gifted, they are right. You are totally normal in feeling crazed over this, but being well informed never hurts anything. There are times when the schools aren't sure what to do and I have been the one to say, hey, why don't you try X, Y, Z and they did! Hang in there, you'll get through it, but I think you should be well informed.
