Your child will be amongst the best and the brightest AND most motivated students in the world. You get a lot thrown at you right from the start and you are expected to perform. For the majority of MIT students, that is just what they want and actually need to feel good. There were lots of “interesting” ways to describe the environment at MIT: “I’ve been here a week and I’m already a month behind” or “Getting a education here is like trying to get a drink of water from a fire hydrant”. MIT will test your study habits and your ego (you can be the top of your high school class and just be average at MIT). It is, however, a great opportunity. You get to study and work with world renowned experts (both current and “to be”) and be involved in cutting edge research.
Visit MIT; do more than just the admissions tour, stop a talk to students, visit a class (you can probably arrange that thru the admissions office). Read the blogs on the admissions website. In other words, do your research (actually, your child should be the one doing all this) and be ready to make an informed decison if your child is admitted.
From what I see, MIT admissions is pretty good at figuring out who can succeed there and those are the students they admit.