At the end of the episode the girls replicate the poster of The Usual Suspects (1995) which is the movie the parents were trying to see and figure out the ending of through the episode.
The scene where Ms. De Brún, the new English teacher, is showing the students photos of former students and telling them that one day they'll be in old photos is reminiscent of the carpe diem scene in Dead Poets Society (1989).
When Erin suspects Jenny Joyce had a hand in getting their English teacher fired she calls Jenny a "super grass". In British and Irish slang a 'grass' is someone who is a rat, snitch, tattletale, someone who tells the authorities information. It comes from the old phrase "a snake in the grass", meaning a traitor. The term "super grass" came about during the Troubles in Northern Ireland to denote a person who gave the British authorities information about the IRA, especially if it was someone within the IRA that did the talking.
The new English teacher Ms. De Brun is mimicking Dead Poet's Society in several scenes.
Nicola Coughlan revealed that in the scene where the clique is walking through the school corridor in slow-motion, Clare brushing over her ponytail with her hand was inspired by Rihanna.