If a story I wrote was published last year in my school literary magazine, can it be published again?
Last year, I wrote a story and submitted it to my college’s “literary magazine,” which is distributed to the student body and also passed out at the Admissions Office. I have since expanded the plot, incorporating what I wrote and published previously into a novel-sized work. If I wanted to have a publishing company publish it, could I? Would it be a problem that part of it has already been in print, before?
There are four possible ways in which your original story could have been published. If you didn’t get compensated in any way, but merely contributed the story in return for getting a published byline, you still own the copyright and can do anything you want with the story. If you were on the staff of the magazine and did the story on assignment, that’s called “work for hire,” and the magazine owns all rights, and can do anything they want with it; you can’t republish it. If you weren’t on staff but were paid for the story, the magazine either bought “all rights,” which means they own it, or they bought “first rights,” which means they bought the rights to publish it once, but you still own it.
But no matter what happened with the original story, it sounds like you’ve added a significant amount to the work, more than likely enough to call it an entirely new work. If plots derivative of previous stories were enough to trigger copyright, we’d have run out of stories a long time ago. 
Feel free to shop your book around, and good luck. Just be sure to tell the publishers it’s based on a work you had published earlier, so they can decide if that’s a problem for them. (It probably won’t be, though.)
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