Skinner's Banks (The Seven Stair Crew Series)

Cale Finch has just won second place in a skateboarding competition when he's ambushed on his way home by a member of a rival crew, the Mental Posse. They steal the money that Cale was going to use to replace his broken skateboard. Cale feels embarrassed by what happened, so he doesn't tell anyone right away.
Eventually, Mark Skinner, an older skater, finds out, and offers to help Cale get the money back. But before he does, tragedy strikes and Mark is killed in a car accident. Cale has to ...