There are no classes on public holidays:

1 January 2018, Monday (New Year’s Day)
1 April 2018, Sunday (Easter Day)
2 April 2018, Monday (Easter Monday)
27 April 2018, Friday (King’s Birthday)
10 May 2018, Thursday (Ascension Day)
20 May 2018, Sunday (Whit Sunday)
21 May 2018, Monday (Whit Monday)
25 December 2018, Tuesday (Christmas Day)
26 December 2018, Wednesday (Second Day of Christmas)