Kind of dangerous to be teaching kids submission holds and such IMO.
As a trained fighter myself, I've seen younger guys who I would train in combatives with end up going to jail for abusing their talents in bar fights.
Hopefully they're just teaching basic grappling skills, which I would see no problem with. It's actually good to know, as it's a lot more effective than throwing fists and won't hurt either party nearly as much.
As far as their age, it's really no different than a kid taking Kung Fu or Karate, learning martial arts at a young age does wonders for a persons discipline and self esteem.