We did it in school, it actually proved somewhat useful - one night when I was about 17 I landed a very effective headbutt on a gropy guy under a bridge, when I was walking to the train station from a bar. I was proud of myself for days haha.

That said while I think sports are great for a multitude of reasons, I am under no illusions that keeping your head on a swivel and running like fuck is the primary thing that would help against hopped-up-on-something attackers on transit. When I was attacked it was because I had let my guard down being in the station proper rather than on a vehicle. Primary for the women they are with it enough to seem to target anyway.