There are several issues here, and none but one of them is simple or straightforward. Unfortunately we don’t have access to Miss Green’s contract with the school, but it could be the case that it contains a clause prohibiting certain type of behaviour. However, it is doubtful that such hypothetical clause would be applicable retroactively, unless there was some duty to disclose information that could affect the performance of the teaching duties. There is not much point of discussing it here because whether they affect or not her performance is a matter of fact, but it is quite plausible that many students were going to be affected in either way by watching the video (some of the actually discovering a renewed interest for the teachings of Miss Green…and by the way, the video has some positive teachings because it is clear that she reaches for a condom before engaging in the casual sex with the builder).
Now assuming that such a duty to disclose does not exist, expressly or by implication, is the video obscene under English law? The parents that are looking for blood may think that Section 1.1 of the Obscene Publications Act 1959, stating that “an article shall be deemed to be obscene if its effect […] is, if taken as a whole, such as to tend to deprave and corrupt persons who are likely, having regard to all relevant circumstances, to read, see or hear the matter contained or embodied in it”, will give them the head of the teacher in a silver plate, but they should hold their horses because it should be noted that in practice the Obscene Publications Act 1959 is used 'almost exclusively against explicit pictorial material dealing with what is generally regarded as deviant behaviour: in other words, sado-masochism, bestiality, paedophilia, bondage, etc' (R Stone, Textbook on Civil Liberties and Human Rights (Oxford, OUP, 2006) at 374) …although there might be some room to consider the video indecent following Knuller v DPP [1973] AC 435 (as Lord Reid said, “anything which an ordinary decent man or woman would find to be shocking, disgusting, or revolting”) taking into account that the fact that the company decided no to air it because being too graphic could prove that was shocking enough.
But, who released it? Was the advertisement company or one of the employees of the one of the constructions company that received it? In this later case we will be talking about copyright infringement due to copying and showing the protected material, as per Sections 17 and 19 of the Copyright, Designs and Patents Act 1988. (where is FACT here?).
But the only issue that is clear from the onset is that we have yet another example about how Internet has changed privacy issues forever: it is not only about your present that you need to care about, is about everything that you have done and has been recorded somehow. We could write a whole blog about what I call Cybersacking (being sacked because something that your employers found about you online even if it does not relate exactly to your job), and it is becoming clear that the temporal boundary of privacy seems not to exist anymore. However, if you go around Facebook and other places where people post things about themselves, most users are not getting the message: be careful what you post because what it seems funny today when you are in college, may come back to hunt you when you want to be a manager…so Internet is not scary, what you do with it might be…
And OK, here is the famous video...(in my case we can argue the educational and/or reporter's exception)