I would say correct it right away.
What breed of horse is he learning to ride on?
For gaited horses the so called chair seat is disered....and is the correct way to ride a gaited horse. Your supposed to sit on your butt and roll your hips backwards...like sitting in a chair.
But on anyother breed that is not gaited...its not correct.
To learn all that a horse could teach, was a
world of knowledge, but only a beginning. .. .
Look into a horses eye and you instantly know
if you can trust him.