I instruct juniors and ladies and have a pair of Remington 1100s in 28 ga. Much less recoil than the 20 ga 1100 with Wally World 20 ga shells. I have a MEC 600 set up for 28 ga 3/4 oz shot and a mild load of Unique. Some of the kids come over to my farm on Saturday and reload shells for themselves to shoot on the Sunday. The 28 ga 1100 with a skeet tube is easy for the kids to hit with and gain some confidence. Reread the latter sentence.
The worst gun to buy a youngster is the Remington 870 Junior pump in 20 ga. I have seen small boys break into tears the recoil is so severe. In fact, I have asked a parent to please put that 870 junior 20 ga back into his truck and let the kid shoot one of my 28 ga 1100s.