If your computer is staying on many days at a time, it may lose connection to some of the USB devices. Thanks to Deep Freeze, a restart will help reconnect your computer to those devices.
NOTE: It's a good practice to shut down your computer at the end of each school day.
NOTE: Most of the newest teacher machines (Windows 10) have been set to shut down at 11:00 PM each evening. This should help with connection issues.