As we understand the current interpretation of the law, a school can, in limited circumstances, show a film in a classroom environment for the purposes of education without infringing copyright. However, it only applies if the audience is limited to teachers, pupils and others directly connected with the activities of the establishment. It will not generally apply if parents are in the audience.
Most schools and local authorities have the freedom to use programmes recorded from the television etc; education establishments are usually covered through a blanket licence agreement from ERA.
The Copyright Designs and Patent Act 1988 (CDPA) includes a number of exemptions which allow limited use of copyright works without the permission of the copyright owner and in this example the school would be making use of Section 34 of the CDPA which states :
34 Performing, playing or showing work in course of activities of educational establishment
(1) The performance of a literary, dramatic or musical work before an audience consisting of teachers and pupils at an educational establishment and other persons directly connected with the activities of the establishment -
(a) by a teacher or pupil in the course of the activities of the establishment, or (b) at the establishment by any person for the purposes of instruction, is not a public performance for the purposes of infringement of copyright.
(2) The playing or showing of a sound recording, film or broadcast before such an audience at an educational establishment for the purposes of instruction is not a playing or showing of the work in public for the purposes of infringement of copyright.
(3) A person is not for this purpose directly connected with the activities of the educational establishment simply because he is the parent of a pupil at the establishment.
You can get more information from the Intellectual Property Office