I'm debating about test-driving a poem at my daughters' school. One of their first grade teachers is a friend of mine, do you think it's overstepping the line to ask if she'd read the poem during story time? I have no pictures to accompany it so it would be a cold read.
In 6th grade, Mr. Zoller would read to us for an hour, and then give us a creative writing assignment, due that Monday (and we'd get to read some of those stories aloud then).
He read to us Where the Red Fern Grows, Stuart Little.... and a story he'd written, and was trying to get published.
I later found the book he had read to us when I was an adult, and tracked him down, and thanked him for letting us be his test audience, and (of course) got my copy autographed.
So I don't think there's anything wrong at all with test-driving during story time, as long as you get the teacher's permission.