St Patrick's Day is an Irish Holiday. Which as far as I'm concerned is nothing to do with Anglo-Saxon culture.
You'd be better with St George's Day for England, St Andrew's Day for Scotland and St David's Day for Wales.
*Edit* Actually I'm not even sure if Scotland counts as Anglo-Saxon either.
True, but I'm under the impression the OP is expected to do by one of his superiors (like principal or dept head) or as an agreement within his group of teachers.