As the husband of a school administrator, I can tell you that the are heavily constrained by their district administration. It is very difficult to be in that part of education and not "fit the mold" (be liberal). The district generally seeks out a conformist to fill that role.
This is because the district administration is constrained by the state and federal agencies who place conditions on the funds from those sources. But most schools cannot refuse the funds, since the local community cannot foot the entire bill for the local district after having to pay into the federal and state bureaucracies.
The root of the problem is the local money is run through the state and federal bureaucracies and comes back to the local district with strings attached.
the dumbing down is no accident...