apple account has been locked how can I fix this?

My Apple account said it was locked for security reasons because of too many incorrect password attempts. When I tried logging back on, it said it was locked and it gave me a link to reset the password so I clicked on the link. After I clicked on the link it said to put my username so I did. Then it said that the apple account doesn't exists. I don't know what to do. Does anybody know the solotion to this? If so, please let me know, please. By the way, it's a school iPad and I can't show it to the school because we're on summer break.