Whitsun
From Tardis Wiki, the free Doctor Who reference
Whitsun was a week's holiday. Barbara Taploe considered it too short a time to travel anyway and instead stayed at Winterborne School planning her lessons.
In 1995, Luke Pendrell was left at the school after his mother and father neglected to pick him up. Christian Purcell (who was possessed by Isaac Greatorex) claimed to be staying because leaving reminded him of the deaths of his mother and father, whilst Andrew Powell had to stay due to his behaviour. (HOMEVID: The Devil of Winterborne)