I think a great compromise would be requiring 18 months of military service out of HS. Everyone goes through the military evaluation, everyone gets trained in firearms. You still have the only people who are actually going to the frontlines as grunts are the people who were already signing up to do that. Every other kid is put into non-combat roles. They learn discipline, leadership qualities and trade skills like logistics, accounting, etc.
Then everyone who passes the mental eval gets out with a license to operate firearms all the way up to automatic weapons.
Then everyone who passes the mental eval gets out with a license to operate firearms all the way up to automatic weapons.