Imagine being those guys. You get your entire gang together and make a huge ruckus at another school, all for the purpose of beating up a single girl, only to have her sandbag the first half of the fight and then destroy you while flirting with her girlfriend. Now imagine looking at that and thinking "Alright. Now it's my turn!" Because you know there's going to be another group who decides to take a shot at her.
Also, I'm really curious about what they mean by "it all began" with the health exam. Thank you for picking this up; I can't wait for more.