My 7 & 8y/o DS's had a poster competition at school. I LOVE to make things and got stuck in to making their poster with them, admittedly, it was more mummy's piece of work than the boys 
although we all enjoyed discussing the topic of "stranger danger" whilst making it so was a worthwhile exercise, plus, THEY WON! Bonus!
I will add, it wasn't to win some extravagant prize, the prize was a pencil case & a hat
After speaking to a colleague, he tells me he had a printing/web design friend submit a school competition entry for his child a few years back!
I'm interested to discover how far you have gone to ensure your child's success of a win at school?!