Once trust has been established, remind these students that you believe in them even if they make a mistake. I've vouched for kids during grade team meetings only to have them get into a fight at lunch the same day. They make mistakes, just like we all do. It's how we respond to their slip-ups that will determine if they'll continue to trust us. Explain that you're disappointed in their actions and that you know they can do better. Don't write them off. Tough kids are used to being dismissed as hopeless. Instead, show them that you care and are willing to work with them. Helping a tough kid overcome personal issues isn't something that happens overnight, but it is a worthwhile investment in his or her future.