Researchers refer to elementary school playgrounds as "gender school" because:

Children reinforce and punish each other for gender behaviors. 

Hope this helps! Have a great day :)

Iam a german monk and professor of theology. i believe that the catholic church's practice of buying forgiveness of sins through indulgences is wrong. i have translated the bible into german to make it easier for more people to be able to study it. i am here to stand by my writings and i refuse your demand that i recant them