I forgot to include a few more sentences I'm not sure of.
Thank you.
1) You mustn't modify or change (?) the marks on your school report
2) You mustn't fake (Or counterfeit) your parent's or teacher's signature on your school report or (how do you call a student's register with excuse notes?)
3) Your must keep your cellular phone switched off during school hours.
4) You must behave properly. You must keep your books tidy (?) and write your notes neatly (?) in your exercise book. You must practise your vocabulary every day and type your summaries into your computer if your handwrting is unclear.
1) The word you are looking for is "alter." You mustn't alter the marks on your school report.
2) The term you are looking for to call a student's register with excuse notes is an "attendance register."
3) You must keep your cellular phone switched off during school hours. There is no alternative term for this.
4) You must behave properly. You must keep your books tidy and write your notes neatly in your exercise book. Additionally, if your handwriting is unclear, you must type your summaries into your computer. There is no alternative term for keeping books tidy or writing notes neatly, but you can use the term "transcribe" instead of "type" if that suits your preference.