Anachronisms: The locker room at the school has a passive Infra red detector clearly visible over one of the doors more recently used for intruder alarm systems. This type of device would not have been available until the early 1990s.
Anachronisms: In the montage scene in the library, at least two books, Michael Burleigh's "The Third Reich" (2001) and Alan Bullock's "Hitler and Stalin: Parallel Lives" (1991), are visible, neither of which had been published in 1983/84 when the film was set.
Anachronisms: The first time we see Hector giving a lift to one of the pupils on his motorbike, they drive past a house with a satellite dish on the wall. Satellite TV did not exist in the UK in 1983.
Anachronisms: The lollipop lady that reports Hector to the headmaster carries a sign that carries the international symbol for children, which has only recently started replacing the old sign that stated "STOP CHILDREN" - which would have been the sign used in 1983.
Anachronisms: In the staff room when Hector says 'French Kiss' to the games master, he is holding a copy of the Racing Post. The Racing Post wasn't launched until 1986, three years after the year the film was set.
Errors made by characters (possibly deliberate errors by the filmmakers): When Posner and Hector are discussing the poem "Drummer Hodge" by Thomas Hardy, Posner references Rupert Brooke's poem "The Solider" by mentioning the line "There's some corner of a foreign field... in that dust a richer dust concealed." The line is actually "in that rich earth a richer dust concealed."
Continuity: Throughout the mock interview scene, Scripps is nowhere to be seen. However, in the next scene when the boys are filing out of the classroom, he's walking along with Rudge and Lockwood.