Seems the debate is do you start with a single shot, and once you master that I'll let you "play" with a 15-22, or do you start where they "play" with the AR styled rifle and then once they gain an affinity for shooting, move them to the more accurate single shots?
I don't recommend doing something just because it worked for you 50 years ago. The kids of today are different. Generally, their attention span is much shorter & they need instant gratification and excitement. Look at the games they play. Guess you have to judge the kids. Most of the ones I've been around lately would benefit from starting with a 15-22 and then once they determine they enjoy shooting, allow them to learn the fine art of accuracy. Assuming they aren't training themselves, we can instruct them to not spray out bullets by the thousand... even when shooting a 15-22. Making a bouncing target, or soda can dance is great fun plus teaches accuracy & controlled shooting.