Let's all check our files and our basements and our offices and our former offices for classified documents. I realize that documents which have been sorted and filed in named folders have been handled. In a sense, they are classified but unless they bear a red stamp that says "Classified document" or "Top secret", we are too busy to worry about them.
If they do have a stamped message on them, take them to the nearest attorney and let him worry about them. In the meantime, you can worry about the size of his or her fee for handling this matter.
No doubt some organization can get a little cash by selling school essays stamped "Classified document" in red ink. Some 3D printers can possibly be used to create semi-serviceable stamps that say "Possibly classified document" and others to clearly mark some of my innocent junior high essays "Not classified document".
Give a little thought to this matter and don't forget your grandparent's attic.