My son is 11, he is kind of tall but small other wise. We got a savage engage in 30-06 for him. The rifle is light, has a VERY GOOD recoil pad, and the stock is an adjustable for LOP. We took all the spacers out for it to fit him. He shoots it well and has no issue with the recoil. I have shot it and it is VERY MILD on recoil. With it being adjustable as he grows we can add the spacer in that fits him, there for he can shoot the same rifle into adulthood. I would focus on a rifle that fits him with a good recoil pad more so than caliber/cartridge. Not saying you should go buy him a 30-06, nothing wrong with .270 Win.(one of my favorites), .308 Win., .280, 7mm08, 260, 243, 257, 25-06, 6mm & 6.5 CR's, and the list can keep on going, many grate rounds to pick from, but I think the most important thing is that the rifle fits him and a good recoil pad is good for young and smaller shooters.