My kid (8) has had several lessons, all from the same person (who he liked, and learned well from the first time), typically one lesson per season. I give him suggestions and technique tips here and there, but I try to keep it limited, as he has somewhat of a bias against taking advice from me. I try to stick to one tip, if anything, per ski day (e.g. upper body into the fall line, or stop gripping your poles like that already).