Just to clarify, I didn't buy electric bike for my son, because I don't think it is good for him. I have no doubts he would be able to handle it without any problems after short period of adjustment..No matter whether it is legal or not or whether an electrical vehicle should be in the hands of a 15 year old.
If it was legal, I would convert bikes for my 10 years old daughters. Unfortunately I can't do that.