Recently Google launched a contest similar to Summer of Code but for high-school students: Google Highly Open. You must be at least 13 and not begun university studies.
You first claim a task from the list and finish it in a given interval of time (usually one week). All participants that submits at least one task receive a T-shirt and for every 3 tasks receive 100$ for a maximum of 500$.
I think it’s a wonderful thing, the Open Source community benefits from this actions while students get experience contributing to open source projects. The tasks are pretty accessible ranging from documentation, translation to code and quality assurance. I participated in GNOME and looking at other projects to see which tasks I can complete.