Birth certificate

Hello, i recently changed back to my birth last name from the last name I have gotten by adoption. i tried to change my names on the records. i can't actually change my name on high school records/diploma. I am trying to get the new birth certificate. Does it necessary to keep old birth certificate and keep both old and new birth certificate? or do i just exchange old birth certificate into new one? since i have still old name on the records, wasn't sure that should i keep both for just in case. or just having photocopy of old birth certificate and get replacement of new one. Thank you.