The following is from the site Medium.com, from their series on inspiring teachers. It looks like a good summary of what HiGA aims to be and some of the history of and rationale for this particular kind of education innovation in Japan.
I’ve heard about Fumi during a discussion with Ota Tamaki about the amazing OECD-Tohoku School project that was launched following the catastrophe in Japan in March 2011, and the Innovative Schools Network 2030 project as a successor project of the OECD Tohoku School with broader participants including Hiroshima. In a few words, OECD Tohoku School is a two and a half year project, in which 100 junior high and high school students from disaster areas came together for workshops. Through this project-based learning, the students organized an event in Paris in summer 2014 to appeal the wonders of Tohoku region to the world.