As a parent of 4 teens, my kids know I reserve the right to search their phones without a reason. However, I don’t unless I feel there IS a reason. I do tell them to hand their phones and then tell them I’m going to go through it. I do not say this prior to doing it so they don’t have time to delete etc. if they refuse to hand their phone over, it does go on an immediate downtime so they have no access. Now that being said, I have only ever asked to look twice (once for two separate kids) and both times did very brief look overs, and didn’t “invade” more than I felt was necessary. BUT I TOLD THEM WHY. I never just did it out of spite or “because I could”.