How do you convince your parents to stop being controlling after a particular age say 15?

There's no way to convince such a thing if you yourself are 15. You perhaps should get someone older who is liberal in his/her thoughts to talk to your parents. Because if you are going to put your case forward that I need a little space and do not want to interfered in everything, chances are your parents will take it in a way that will not ease the situation. I guess, make your elder sibling talk to them. And if not that, you can have a friend's mother or father (who are different in their approach in dealing with teens) discuss the matter generally over a cup of coffee. This way, they can have a different perspective about how there are other ways of dealing with teenage kids. Hope that would help.