I believe this is "Like Minds" by Robert Reed, first published in the Oct/Nov 2003 issue of Fantasy & Science Fiction, and collected in the 2012 anthology Other Worlds Than These.
The main character does in fact trade a high school essay for an award winning novel, as seen in these quotes:
Then Josh says, "A book, a novel."
Words cause a multitude of realms to work together, the Authority suddenly engaged. A deceptively quiet voice asks the obvious: "Who is the author of this book, this novel?"
Josh can say any name. But he takes a deep breath and blurts, "Me."
"Are there other criteria?"
"Like what?" Josh had thought that he came prepared, but he feels sick with nervous energy, almost too anxious to think."
"I pick random examples," the Authority cautions. "But you may narrow the category in significant ways. For instance, what is the author's age? How well did this novel sell? And did the author win any awards or commendations?"
"Awards?" He hadn't quite thought of that. "You mean, what...like the Nobel Prize?"
"Okay. I wrote the novel in my thirties, and I won the Nobel Prize and the Pulitzer, too."
He also gets memoirs of a version of himself that became world leader, and a porn video of himself in a threesome with a hot classmate and his algebra teacher.
"You must give your gifts now, sir. Since you are requesting three examples of your genotype's accomplishments, you must surrender three works from your own life and accomplishments. Please."
This can be a trauma. Sometimes the client examines his own gifts with a suddenly critical eye, and all confidence collapses. How can a tiny soul measure up against Nobel winners and God-like despots?
But eighteen-year-old boys are blend of cockiness and unalloyed ignorance. Without hesitation, Josh pulls three offerings from a long gym bag: a fat rambling term paper about the role of robots in the War of Ignorance; an eleven-page story about a misunderstood adolescent; and a comic book written by him and illustrated with help from a popular software, the superhero wearing Josh's face and his unremarkable fantasies about violence and revenge.