Our school teacher didn't go to the dormitory to see if the students were sick, so he told the guide that you had a headache, or caught a cold, or sprained your ankle playing ball. In this case, the teacher will usually give you a note. If the teacher is strict, get on well with the doctor in the school hospital, buy your own medicine and ask him to give you a certificate, and then tell him not to write the date and year, and take one part at a time.