Follow the money.

The superintendent wants his job, and control, he reports to the board.

The principal wants his job, and control. He reports up, but he is in control of the local teachers and can exert direct influence.

The level of conservative or liberal slant of the school typically depends on that, under the total guidelines from the board but it takes a long time (if ever) to force any change from below.

Individual teachers and courses enforce selective pressure. History, psychology, sociology are wide open for left or right attitudes. Math, not so much. Science is usually on the left, but an occasional righty will slip through.

The last thing any of these people want is an INCIDENT. They will sweep anything under the rug that they can. This gives extra power to any of the aggressors in these situations, up to the point of media explosion.

At that point they may be forced to do something.