Be A School Hero Badge Design Needed

Hi, we've built a platform that will enable anyone to sell their stuff via a new style of raffle. The site is www.raffle.it. You can see our current style and logo there. This particular project relates to a specific area of the site www.raffle.it/school - these raffles are played by individuals on behalf of their local or children's school. Whoever wins donates the prize to their preferred school. Anyone can play and in a sense become a School Hero.

We're looking for a simple badge/logo that players could display on their social network pages/blogs etc.

We'd need to print this on large posters too so the finished product would need to scale up to A3.

I have attached a very bad sketch but am open to alternative suggestions. Bright colours would be good, perhaps boy/girl variants.