Kids are sometimes late to class and when kids are late it disrupts the teacher and students. Kids are late for many different reasons. Sometimes they are messing around in the halls, they are in the bathroom, or they are doing something else that causes them to be late. When you are late you have to go get a pass and call home. Then you get a behavioral refocus and get marked tardy.  

Kids who are often late might have a lower GPA; they also might have lower scores on standardized tests. According to a study, kids who are often late to class might get suspended more often than kids who are not late. Also if kids are often late to school it starts a bad habit and it could lead to people being late to work and getting fired. 

When kids are late it disrupts the whole class. Some kids get distracted by the interruption. And the teacher sometimes has to ensure the late student is caught up on work. Based on the research you should always try to be on time for class.