Snakeman

The Snakeman and his gang are terrorizing Portland High School. When he demands his weekly 'dues' from Cathy, the new girl at school, and threatens to hurt her or her younger brother if she doesn't pay, she decides to do what he says.

Her tactic of non-resistance works well for a while, but when she notices that he wants more - first her jewelry, then herself as his girl and partner - she is ready to fight.

It's the classic David vs. Goliath situation, in which Cathy has the feeling that she is facing not only the Snakeman and his gang, but the whole school, which seems to be in the power of the gang