I've had this problem before
I made a file with nine artboards- one for each part of the project- and after finishing two parts (one on each art board) I saved it to take home. Once I open the file I only see the first part I did
Sounds like something is corrupted. My advise: at school create a simple new document with multiple artboards and check if you can see them at home. If you get the same problem, you may have corrupted preferences which will require resetting the preferences. If there is no problem with the new file this means only the original file is corrupted which will require to copy its content, paste it in the new document and recreate the artboards.