The relationship between students and teachers is less formal in the USA than in many other countries, especially at the college level. American college students do not stand up when their teachers (1) the room. Students are generally encouraged to ask questions in class, to stop in the professor's office for extra help, and to phone if they are absent. Most teachers (2) students to enter the class late or leave early, if necessary. (3) the lack of formality, students are still expected to be polite to their teacher and fellow classmate.
When students want to ask questions, they usually (4) a hand and wait to be called on. When a test is being given, talking to a classmate is not only rude but also risky. Most American teachers consider that students who are talking to each other (5) a test are cheating.