It depends on the instructor. Some will push students through quickly just to keep their business up - kids who want to be cantering and jumping asap and parents who think cantering and jumping means their kid is talented.
I think this is a money hungry, useless way of teaching to be honest, as the student does not know the basics and when sh!t hits the fan the kid can't stay balanced and stay on board.
I start them very slowly, teaching work on the ground so grooming, tacking up etc. General horse common sense, mounting, position, 'stop, go and turn' etc. I lead the student for a few lessons so I can stay close in case they lose their balance, before they go out onto the lunge.
I much prefer them to be totally comfortable on a horse, confident and capable at 'stop, go and turn' CORRECTLY -yes, even 10 year old kids can use their seat to control the horse. If you teach it early, there's a much better chance that they'll retain the information for future riding.
You can't put a time frame on learning. I'm absolutely still learning and I compete, coach and train regularly. Internationally competitive grand prix riders are still learning.
As has been said above, everyone learns at a different rate, and feel that putting a time frame on a person to achieve things in their riding is unfair, as if they do not meet that time frame they feel down about themselves and their abilities.