Is there any way that I can claim a piece of writing is mine, without having to copyright it?

I've written a story that I would like to send to a person through either post or email, but in both instances I wonder if there is any way that I could make it clear that the document is mine and that it must not be edited from that form. I know that a copyright does all those things and more but I don't want to have to take a copyright out since they are not important pieces of work, just some stuff I did at school... but I still want it to be clear that it's my work. I could of course sign what I send but that could easily be erased or edited out.

Any suggestions?