The Boston Review has a special issue devoted to the question of what foundations are for.
The lead review describes the role that foundations are supposed to play: to encourage innovation, to prod government to change its priorities, to demonstrate the validity of a different path, etc.
Various commentators, including me, were invited to respond. I tried briefly to explain how the role of foundations in the K-12 sector have changed in significant ways. The three biggest foundations now act in concert with the U.S. Department of Education, not trying out new ideas, but imposing their shared ideological agenda. By he power of this combine, they actually exclude and repress any thinking other than their own.