Choose the correct modal verb

1. You
   [should|need] to ask your teacher if you require extra help with your studies.
2. You
   [can|must] raise your hand and wait before you ask a question.
3. You
   [mustn't|don't have to] do this homework assignment, but those who do will get extra credit.
4. In Britain, all teens
   [have to|may] stay in school until they are sixteen years of age.
5. In the old days, teachers
   [could|should] hit students with a ruler if they misbehaved in class.
6. In certain schools, students
   [may|must] stand when their teacher enters the room.
7. You
   [should|might] spend more time studying if you want to get good marks.
8. Steven wants to go out with his friends but his mum said he
   [needn't|can't] go until he has finished his homework.