Well, all boys are different. But, i can tell you that 5'8" is the average, with a norm of 5'3"-6'0". That doesn't mean that everyone is in this range. Sometimes, a 14 year old can get up to 6'5" (!!), whereas others may be barely 4'6" (!!). It really does vary. But, just about everybody (95%) is going to be in this range. Hope this helped.
The Height Expert