I've been teaching now for about fifteen years. I have two kids myself, but the best birth story I know is the one I saw in my own second-grade classroom a few years back.
When I was a kid, I loved show-and-tell. So I always have a few sessions with my students. It helps them get over shyness and experience a little public speaking. And it gives me a break and some 'guaranteed entertainment' Usually, show-and-tell is pretty tame. Kids bring in pet turtles, model airplanes, pictures of fish they catch, stuff like that. And I never, ever place any boundaries or limitations on them. If they want to lug it to school and talk about it, they're welcome.