There are a few reasons, and often it only "seems" as though they do. For example, sometimes when a really jittery (talks a lot, doesn't listen, moves around) kid asks to go to the washroom, I let them anytime for two reasons. 1) it allows the rest of us the peace to get the important points out while he is gone and 2) sometimes all the kid needs is a walk around to burn some energy, because some kids just can't sit for so long. I may not let another kid leave, because what I'm saying is important and I want them to listen because I know they can. Also, often the troubled kids are ones that have few close relationships. They often don't have receptive parents, most of the kids find them annoying and the teachers only want to teach the good kids. I go out of my way to be nice to these kids, listen to them, and help them because if you can get them on your side the semester is a lot easier than if you fight with them day in and day out. Also, once you have these kids as an ally you have them forever. They seek me out even when I'm not their teacher anymore for help, guidance and just to tell me what they're up to. Not only does it make me feel good, it is good for them to have an adult they trust in the school that can guide them down a better path than they might choose if they were on their own hating authority. It may seem to be favourtism to other students, but ultimately, it helps the class as a whole, it helps the troublemaker and it helps the teacher. It may also further help the community in that having a trusted adult in a troubled teen's life could help them steer clear of the bad things.