But it’s their property, their business covered by their insurance at their cost and therefore their decision, BTW.most don’t count riding when you are 5 years old to around 9 years old as the kind experience that would qualify you to jump alone. And you are still a minor.
After you’ve been in a barn and they get to know you well, you can sometimes be allowed to take a few jumps but only if other clients don’t see you and you keep your mouth shut. Otherwise if you do it all others will want the same privilege.
Just a reminder here, be careful how you present yourself when looking for a barn. You come off as rather entitled and proclaim yourself superior rider with superior knowledge. Won’t endear you to future trainers and barn managers, barn mates might not care for that attitude much either.
Find a barn with rules you agree with, don’t pick one and demand they change for you.