The law expects teachers to be reasonable. “Reasonable” and “reasonably” are spread liberally through the law like currants in spotted dick pudding. In health and safety cases, where the school’s duty of care is under scrutiny, the test is sometimes “the ordinary reasonable teacher”, but courts still use the ancient test of “what would a prudent parent, who knows something about the circumstances in which the behaviour in question took place, have done”? In employment cases, appeal tribunals have suggested that the words “reasonable” and “unreasonable” should be interpreted as including “having regard to the applicant’s Human Convention rights”, where there is a clash between working life and free time.

Then there is “Wednesbury reasonableness”, a legal phrase that lawyers bandy about. It began with a 1946 planning case in which a judge was asked to decide whether the decision by the council (a public body) in making a planning decision was reasonable or not. The judge concluded that to be unreasonable, a public body would have to have done something that no person in their right mind, and in full knowledge of the facts and circumstances of the case, would have contemplated doing - which sounds as though a public body would have to be slightly mad to be unreasonable. But it still applies to maintained schools, which are public bodies.

Nowadays, courts will not try to second-guess exactly what a reasonable person would have done in the circumstances. They will decide whether the behaviour of the parties was “within a range of reasonable responses”.

Chris Lowe, Former head, now chief editor at Quick Guide Publishing.