I was getting my ass kicked more frequently in public schools, so my parents moved me to a Christian private school. The school board mandates x hours of physical education per week, but the school was smallish, and didn't have a gym.
Every Wednesday we would hike down to the nearest public rec center. The rec center was a fairly good size, so we had the option of multiple things to do -- volleyball, kickball, whatever, all spread out on separate fields. This meant that the teacher(s) would rotate from one field to the other to keep an eye on things, which invariably meant that any given field was only monitored about a third of the time.
I never believed in team sports, because of this - if we were playing volleyball, for example, and I made a good serve, somebody on the other team wanted to kick my ass. If I made a bad serve, somebody on my team wanted to kick my ass.
I later moved from Hawaii to Tennessee, for my junior and senior years of high school, where, due to my athletic build and coordination, I was sought after by all the coaches for all the sports teams, but I hated sports. I'm over it now.
Summer break came around, and I enrolled in Judo, Boxing and Muay Thai classes. I took an under the table job in construction to pay for the classes. I stole a kayak to get to work. Every single activity in my entire life was focussed on getting better, so I wouldn't get my ass kicked.
I jogged, lifted weights, exercised, trained, etc. I was Rocky. I was the Karate Kid.
When school resumed the next year, the first Wednesday, I got into a fight. I didn't lose. I wouldn't say I "kicked the other guy's ass", but I didn't lose.
After that, i didn't get into nearly as many fights. I was no longer the easy target. And there weren't any other white kids in the class, so much of the violence stopped altogether.
I'm sure you could potentially attribute it to the bullies being a year wiser, or any other number of factors, but from my experience, this argument holds water.