At what age did your parents stop checking your phone to see what you have been up to? Or what age did you stop checking your children's phone at? My parents still keep an eye on mine at 19 years old.
They didn't check my phone at all but my dad occasionally tried to punish me by taking my phone away. Only because I was always late for school lmao but I would always end up finding his hiding spot anyway.
I never had a cell phone growing up, didn't get one until I was in my 30's when my wife (then girlfriend) gave me one for Christmas. It was not beyond my mother to listen in on the extension when I was talking to someone though...I always heard when she picked it up.