We ... behave well.
must
We ... listen to the teacher.
must
We ... come late for classes.
mustn't
We ... be noisy.
mustn't
We ... put the hand up to speak.
must
We ... fail the test.
mustn't
We ... mustn't bully other students.
mustn't
We ... take part in project work.
must
We ... interrupt other students.
mustn't
We ...come to classes on time.
must
We ... work together with the class.
must