As High Wing Drifter says though, being charged for a no-show certainly does sound a bit harsh, especially as it was due to circumstances beyond your control.
Come on!
Cancelling due to weather is (if you're due to fly solo) proper exercise of a command decision and should not attract a cancellation penalty.
Cancelling due to deciding that you're not "fit to fly" is a legal requirement and should not attract a cancellation penalty. This will happen to everyone sooner or later, and the school should factor the costs into its normal charges. Giving people a financial incentive to fly when they're too ill is, after all, insane.
But if you cancel because:
(1) you forget about the lesson
(2) you can't be arsed to turn up, whether or not you can be arsed to phone up and tell them
(3) you fail to make adequate transport arrangements to get yourself to the airport (whether because you fail to maintain your car to roadworthy state or for any other reason)
(4) you've still got a hangover from last night
then that is hardly the school's fault, and it's hardly an inevitable natural disaster, so why should the school, and hence other students, bear the cost?