If he's just starting out, it may be good to set the seat low enough so when he bails during the learning stages the seat won't jam him in a certain spot, or send him flying... Too badly. It happens. Then when he gets to the point where he can roll around on his own without a wall or rail for support, he can always raise the seat to where he feels comfortable and doesn't stress his knees...To the height konaman recommended. He should be able to figure out his prefered seat heigth once he gets a feel for things.