I was a high school junior when I walked out of Titanic, right at the "art book" scene in the beginning. It didn't take rocket science to know what was coming next. I should have walked out of my Best Friend's Wedding too. (Ironically a neighbor told me to walk out and watch Air Force One next door....but I didn't because it was "R", and honestly, it was probably the better choice...)
So, yeah, I screen my PG-13s too, but I'm not #1 conservative.