That's probably why there is apprehension on their part Just because everyone is doing it is the wrong reason to get the piercing You need to explore why YOU want it I personally find them unattractive
You know I am thankful for some of the things my parent told me I couldn't do when I was your age. Just listen to them and when you are 18 you can mutilate your nose if you still want to. (My guess will be you won't)
I don't think in the 7th grade you'll ever be able to convince your parents, and rightfully so. wait. think long and hard about it, and when your old enough and don't need permission and if you still want one get it then. in the meantime, rhinestone appliques can be used. the look without the hole.
This is one of those things you need to be older and more, way more, mature before you make the decision. This will mutilate your body permanently. Can you see a successful doctor or lawyer with a pierced nose arguing in front of a judge, or performing surgery...I can't.