Humans are just highly intelligent animals. Kids acting like animals when they are 5 years old is not unnatural.
[1] https://www.houstonchronicle.com/local/gray-matters/article/...
[2] https://www.scholastic.com/teachers/articles/teaching-conten...
https://www.steinereducation.edu.au/steiner-education/early-...
It's not like parents aren't motivated to change their children's behavior to be more manageable...
I believe that sitting children down for a couple of years, compulsory, is a strong factor in what we call civilization and the overall decrease in violence. You can think of it a bit like Zen's "just sitting" meditation practice, if you want.
My kids' daycare has adopted it. It seems perfect for my daughter who seems self-driven, but maybe too open-ended for my son (who we pushed ahead..so far - mid-november bday with 10/31 cutoff).
Or maybe better: https://www.montessori.com/montessori-education/
EDIT: I'm talking about drugs like Ritalin.