Have you tried contacting the school? If you have no recall of even installing the software then it might be difficult to convince anyone that you own the rights to use it. Here is a link you can use to chat with Adobe support to see if they can offer any information.
Serial number and activation chat support (non-CC)
http://helpx.adobe.com/x-productkb/global/service1.html ( http://adobe.ly/1aYjbSC )