I must have very lenient parents because my brother was watching James Bond at 10.
I don't care for James Bond, although if you force me to watch a James Bond movie, I'll watch The Spy Who Loved Me in a pinch. The Bond girl in that one is bad ***.
Mine didn't have too many strict rules. No PG-13 movies unless they were pre approved until I was about 12. By the time I was in high school, I knew enough to self censor, so there weren't any rules. I just knew they probably wouldn't be okay with R rated movies with lots of sex scenes. Other than that, they basically just let me choose entertainment for myself.
My mom even let me watch When Harry Met Sally at 13. There's just one particular scene that she skipped...
Keeping in mind I was a rather mature teen who didn't sneak around, so they didn't feel the need to censor my emtertainment. They just trusted me to be responsible.