YOU SAID:

if the teacher does not arrive within 15 minutes we are all legally allowed to leave

INTO JAPANESE

離れること私たちができるすべての合法的に先生が 15 分以内に到着しない場合

BACK INTO ENGLISH

If you do not legally arrive within 15 minutes all legally we can leave

INTO JAPANESE

合法的に15分以内に到着しないと

BACK INTO ENGLISH

We have to legally arrive within 15 minutes

INTO JAPANESE

私たちは合法的に15分以内に到着しなければなりません

BACK INTO ENGLISH

We must legally arrive within 15 minutes

INTO JAPANESE

私たちは合法的に15分以内に到着しなければなりません

BACK INTO ENGLISH

We must legally arrive within 15 minutes