You've obviously never worked with 7th grade girls
There is a transition that happens in the 6/7th grade for girls that only people who have worked with them can see
boys are "boys" from day one and change to become men (at least most of them do) (one transition)
Girls are different
They are kids, until nature slaps them in the face with the fact that they are girls, then they become women (Two transitions)
most young girls are girls from the gitgo, but I'd say for about 25% of them it doesn't register that they are girls until they have to acknowledge it by either nature, or chronological aging
I'm sure I will get negative and defensive feedback on this,,but I am 43 years working with over 2000 girls/women and my insight is learned, not supposed
That said, a good coach can judge the potential of staying power and potential at this age
BUT NOT before!