How about North Dakota? I had a coworker that just could not get enough sex, she was in her early 30’s. She was proud of it and boasted she was on birth control pills since age 13.
I’m certain in order to get the pills the parents had to know it and approve.
Most teen girls are on birth control which is started soon after menses.
It is used to regulate lighten or remove menses to a 2 or three time a year occurrence. And of course prevent pregnancy. High-schools and planned parenthood and family doctors are the sources.
One cannot be in the room with a teen when visiting a doctor these days.