Do you know about Me to We? It's an organization that is associated with Free the Children that asks young people to make local changes for a greater global impact.
Me to We has lots of resources for teachers on their site, as well as pre-established campaigns you can run at your school to raise awareness and money. I think it would be really interesting to challenge kids to come up with their own campaigns. One thing I know about young adolescents is that there's nothing that gets them more fired up than injustice. The opportunity to make a difference in a social justice issue would be an incredible learning opportunity, and would be an amazing way of noticing character in context.
The design thinking process would be a perfect process to use to have kids find an issue they care about, ideate solutions, and come up with a prototype for them to test.