He may have also just been really good at it, it may not be that he was jumping really young, but that the height didn't matter, so they let him jump bigger. 5 is about the age young jumpers with mucho talent can start to jump bigger, I think, but it's true that you should wait till they are about 4 before going above cross rails and that's on the young side. I wouldn't school over 3 ft often, but I can't hurt to have some fun once in a while, as long as both of you are enjoying it. Bigger than 3'6 at 5 is dangerous IMO.
Troubled TB ~"A thorn by any other name will prick just as deep." @-'--,---