If the face plates inside the controller can be removed, do so and store them safely inside for the winter. Steel wool should be stuffed into the wire conduits entering the base of the controller from the valve box to prevent mice from nesting in the box for the winter and having a party with the multitude of wires inside. Many superintendents place a few moth balls in the base of each controller as added insurance against mice. The school is out on whether to leave the power to the controllers on for the winter. What is generally agreed upon is that the power should not be turned on and off throughout the winter. That same freeze/thaw cycle you dread taking place on your greens can also wreak havoc with the components in the controller. For what it's worth, I used to religiously leave the power on to the controllers over the winter. One year the main power switch to the entire front nine of the irrigation system was inadvertently turned off when an employee forgot to turn it back on after some late season maintenance to the system. Thank goodness, because during a mid-winter thaw one of the controllers became immersed in over 4 feet of water. Had the power been on, the resulting damage could have been very expensive to repair.
Taking a few minutes at the end of the season to properly winterize and maintain some of the key components of your irrigation control system may wind up saving your department and your club a lot of money and a load of stress in the seasons to come.