You may make a request for your transcript showing grades, attendance, and number of credits from the high school you attended. (After three years, you would need to contact the school district's records department to make the request.) The school counselor (or in some cases, registrar) would be the person to whom you would speak.
If you need an official transcript for college admission or admission to post-secondary training, contact the counselor at your high school. There is a release of information form you will need to sign giving them specific information about the address, etc.