We were started by age five with a BB gun. Allowed to shoot .22s and .38 specials with close supervision, even at that age. Graduated to a Sheridan pellet rifle, then a .410, then a 12 ga, all before we were presented with our own .22s. Dad reasoned the .22 had more potential for hazard versus a shotgun primarily because of how far the .22 bullet can travel.
So, we grew each hunting season. Dad had a goal. By the time we were 16 and had access to cars, he wanted to be sure we were good to go regarding our education on firearms. By that age, we would go hunting with our buddies after school without adult supervision, and since we'd already had a lifetime of safety training from dad, it was no big thing. Long before I got to 16 my little brother and I would hunt all day without an adult within miles of us. We knew what was expected of us, and we followed the rules.
I shot 3-position smallbore competitions from age 14 on, so by the age of 16 I'd literally fired thousands of rounds of ammunition.
Of course, although I'd rather not consider myself a fossil, times were different then. Lots of my friends and I would have guns and ammunition in our cars in the school parking lot. That way we could head straight from school out to the marsh or fields. We never, ever had an issue with guns at school.