Outside of the observatory on the tower Plato and Jim run into Buzz and his friends and Buzz and Jim begin to fight with knives. At first Jim did not want to fight with a knife but picks up the knife and starts to fight when he is called a chicken for not wanting to fight. Another time being when Jim is called a chicken and challenged to a chickie run he goes to meet up with them and race just because he would be able to prove that he wasn't a chicken to them. Jim went as far as risking his own life to prove he isn't a chicken. Jim will do what whatever it takes to prove he is no chicken because of his insecurity of becoming his dad.
In the beginning of the movie we learn Jim and his family have moved from place to place to allow Jim to have a new start in his life. We learn that Jim is tired of running away while his mother sees no wrong in it and so when Jim encounters a new issue this time around Jim's mother wants to move but Jim wants to stay and face his problems instead of running from them as he is usually does. When his mother first tells him they are going to move again Jim stands up to her and tells her that they can't and that he must face his problems because he set on facing his issues this time around.