A leaving certificate is usually a formal document, so it should ideally be presented on letterhead. Although you wish to convey that the distance between home and college is too far, you should still format your certificate as usual meaning that it should have the subject's full name, date of birth, date of admission, grade at admission and grade upon completion, and reason for leaving. If your reason for leaving is distance, then you can add this here. If this is not your reason for leaving, add this on at the end of the above information. You should also have the head or principal of the school sign your certificate.
