According to Maisie Williams, director Carol Morley instructed Maxine Peake (Eileen Lamont) to not communicate with Williams (Lydia Lamont) and to keep her distance from her, in order to replicate the lack of relationship between their characters. Morley did not tell Williams about this, which left Williams feeling disliked and upset throughout the shoot due to the way Peake was ignoring her. Williams eventually found out about it during the wrap party after shooting had ended, when Peake told her about Morley's instructions and apologized for any upset caused.
May have been influenced by a real life mass fainting at Hilda's Girls' School in Blackburn, England in 1965. The film is set in 1969.
The poem in voiceover ("There was a time when meadow, grove and stream...") is "Ode on Intimations of Immortality", written by William Wordsworth between 1802 and 1804, and published on 1807.
Florence Pugh (Abbie) is a singer songwriter in real life.