Whenever I think about the rude behaviors of students in classes, I always consider how teachers and professors feel about and react to student's behaviors. In my own country, Japan, it is taken it for granted that students respect to teachers and professors, so that almost all students in Japan do pay careful attention to their lectures without talking during classes. Because of this, during classes students in Japan are very quiet and eagerly take notes. Also, even teachers and professors seldom bring foods or drink into classrooms mostly because they think they also have to have some sort of respect to students who are willing to listen to their lectures. However, in schools in the U.S the situation is completely different.
Students eat some snacks and drink beverages stretching their legs.
Moreover, some of them start to pack textbooks and notes into bags and try to leave before classes are over. The students in the U.S are not likely to be aware that they are learning from teachers and professors. In addition to that, they tend to think that students and teachers or professors are on an equal footing, which prevents students from respecting to teachers and professors and makes students act rudely. Therefore, above all, students have to bear in mind that since teachers and professors teach them, they must pay respect to them.