Have you tried clipping the flight feathers on one wing of the younger ones to keep them on the ground?
I have a pullet that must have broken her wing at a young age and I didn't notice it. She is healthy and happy, but when I let all the girls out of there jails this one still tries to fly out and usually she either flies into the gate or does a roll over and hits the ground. Years ago I had chickens and clipped just one wing and mine couldn't fly. Kern
We raise our own quail and ducks. Probably will do the same next Spring if we decide we want more chickens.