Elmore in his insightful School Reform from the Inside Out book says,
The good news about existing reform strategies is that they tend to galvanize commitment among the already motivated by concentrating them in small groups of true believers who reinforce each other. The bad news is that these small groups of self-selected reformers apparently seldom influence their peers.
It's hard not to interpret ideas like this in terms of multi-level selection theory: people tend to be drawn to self-reinforcing, adaptive groups which have evolved protection from freeloader and dictatorial abuse.
What Elmore is getting at is that educational reforms can delve into core practice change at a small-group level but can only broach superficial change at the large-group level. The large-group level of education is a juggernaught.