From elementary school all the way up through high school, students have this "can't wait to get out" attitude. This also coincides with kids acting up in school. Throughout the younger years it isn't so bad because there's not that much of a serious disturbance that a twelve year old kid can make. However, as kids get older and earn more privileges and responsibilities, the kids that are troublemakers are a bigger problem.
Such kids can be a constant disruption to their class. Teachers shouldn't have to put up with a student constantly causing a disturbance in the middle of their teaching. It not only slows down the pace of the class, but can make the teacher mad and give him or her unnecessary stress. Even if the student isn't disrupting the entire class, their actions may make it hard for other students around them to learn which isn't very fair to the other student.
Some students go to school to learn but can't because another person is causing problems in the classroom, and something has to be done so that the kids that want to learn can get their education.
Students who leave either class or school without permission are causing problems as well. Kids who leave class can cause problems in the halls and force hall monitors and teachers to go out of the way to stop any more disturbances. Very often kids will be rowdy in the halls while a class is being taught, and the teacher has to either go over to close the door, or will go out into the hall to try and discipline the kids. Another problem is when kids leave class they could be vandalizing stuff in the halls. The custodians who work at the school shouldn't have to clean up after...