Under Illustration for Instruction (section 32) One can use extracts from: films, sound recordings and broadcasts as well as text, music and artistic works in lecture slides to illustrate a teaching point. Fair dealing applies. There is no statutory definition of fair dealing. It will always be a matter of judgement; what would a reasonable person consider "fair" but you should ensure sure that:
You may also use extracts for the purpose of setting exams.
Any materials used should have been legally acquired.