My son will be 12 next week, and I am sure that within a couple of years he'll be well on his way to being as tall as his father (6'2"). We recently bought him a queen-sized bed because of that. We all tried the mattresses, and settled on a relatively soft one for him. It does feel very good--and the latest evidence I've heard cited shows that super hard mattresses aren't all they've been cracked up to be as far as good for your back when you're sleeping.

The up side to this big of a mattress now--with all of the stuffed toys plus the two cats who hop up with him at night, there's still room for the kid.