I'm 15yo and I keep simple secrets from my parents like what gifts I get for them or sometimes I won't talk about my life with friends(not that I do bad stuff with them, it's just that we do and share a lot of personal information). Now, I've kept some major, harmful and terrible secrets from my parents and let me tell you, the truth ALWAYS comes out; no matter what. And some secrets(no matter how personal or embarrassing they are) can be harmful if not to your parents but you! TL;DR: learn the difference between a harmless and a harmful secret; if it doesn't feel right that you know something and your parents don't, tell them!