Dont think its just boys..perhaps the adjusting to changing body shape..one thing that was suggested here was tailoring the activity..which meant staff had to retrain..
I was a good all round athlete and around 12/13 was beaten in a race on sports day.My changing shape (hips bust) slowed me .I remember being amazed someone beat me.I even remember who it was.I had to work harder to do what I had been doing.This girl was not yet menstrating and faster.team sports builds such camaradarie that its sad some girls loose out.
I danced right through my teens and soon reached an understanding of my body changes.
Whatever I hope it is worked out.I still get a rush moving my lawns..nothing is quiet like loving using my body well.
Due to my arthritis I have to judge how much I do.Pacing myself.
MA