must be, must study, musn't have, musn't run , should be .
1. Boys ........ long hair. Please do not wear baseball caps. 2. You .......... inside the school - it's dangerous. Please walk. 3. Students ........... polite the teachers. Students will be suspended for bad behaviour. 4. All students ........ English and maths. These subject are compulsory. 5. Morning classes start at 8.45 a.m. Students ........... in school by 8.30 a.m. , if possible.