http://i.imgur.com/Qpoth.png
I'm not sure because the style doesn't seem quite "Watterson" enough, although it has his name and a syndication marking on it. If it is real, then it is very depressing.
No way Watterson would do a comic like this! xDD Have you noticed that in all of his comics, Calvin's never the one to do any work? And the signiature mark looks a little fake. This style doesn't exactly look like his either.