How young is too young?

Amber • 7/1/09 miscarriage (8w2d), 5/31/10 my son was born, 5/26/15 chemical, 6/24/15 chemical.
Some of the posts here (on the app in general) make me want to strangle people. 
Why are kids that are 12-13 on this app? 
I don't know about the rest of you, but at 13 I was still going home after school to change, then go out and play. I wasn't worried about my vagina being loose, or if I was having too much sex, because none of that was going on. 
Why are kids SO focused on growing up so damn fast? It's scary as shit. I work in an elementary school and it makes me fear for my own children. O.o