My creative talents were pushed to the limit at the weekend when my large haired eldest presented us with his homework. Make a working model of a sperm!!!! Several plastic easter eggs, ping pong balls and papier mache later, ta da........ a beautiful sperm. I don't remember doing this when I was 11. Apparently one child's sperm model was as big as a chair..............that's a hell of a lot of papier mache!