My son is not a holdback. He is a 2020 who meets the us lacrosse guidelines for u13. I am comfortable with him playing against older 2020 kids who may be older so I am fine with him playing in the aa division. If I wasn't I would have signed him up for another team that played at a lower level. When your son tries out for a club they tell you what types of tournaments you are going to and the types of opponents they will play. If you don't like the answer pick a different club instead of whining.
The idea that you can't figure out in advance what types of opponents you are going to face is silly.
Good luck on u13 with the 15 year olds this summer.
When the tournament you registered in doesn't have enough teams to make your AA Bracket, what happens then?? I bet the team that entered into the B Bracket has no say when all of a sudden they are playing againt those bigger/cheating AA teams.