If your kid can play...another factor to consider is what they get exposed to by playing Varsity ball at 14 or 15. They get to hang out with 18 and 19 year old young men who do what young men of that age do.
There is a whole new perspective on young ladies and the introduction to drugs, alcohol, language, attitudes etc. that can have a significant impact on a younger player who isn't prepared to block it out.
These older players may have a lot of sway since they might be among the coolest guys at school and your freshman or sophomore can gain a lot of status if he is considered cool by those guys.
So looking back if I had it to over again...I wouldn't have held mine back not so that he could play earlier in his career....I would have held them back so he'd be more prepared for the junk. I'd also have considered moving him up to 14U ball at 12 so that process could begin and he could have been more prepared.
Or, he might get exposed to kids that really know how to play at an advanced level, show the effort level it takes to be a great ball player, take AP classes and focus on studies after practice, etc. Not all high school juniors and seniors are kids I don't want my kid around. In fact, most of the advanced ball players I see are very hard working decent kids.