I always prefer to start them with a bolt action. Savage makes some good starter rifles, I would go with the ones with the box magazine as the other magazines tend to have sharp edges.
I’m really loving a little Ruger American II ! Mine is in .308 and it’s very accurate. The stock is adjustable for comb height and length of pull via extensions so it can grow with the teen. It’s offered in several different cartridges and a few different configurations.
I think a great first gun for a kid is a single shot .22. There is nothing scary about it, i.e. no loud noises and no kick. And a single shot means they are forced to learn to aim carefully and make every shot count.