We’ve all seen the fly-on-the-wall documentary where people are followed everywhere by the camera. Well, teaching’s like that, except, instead of one “camera”, there are 30. They’re called children and, like the documentary film-maker, they watch, weigh, edit and then decide which bits they want to broadcast. Usually to their parents or other teachers.

Teachers are often surprised by how much parents know about what happens in school. And parents are sometimes unhappy about what they know. “Telling my boy he’d have better manners if his parents weren’t so uncouth isn’t what I expect from a teacher,” a parent once complained to me and I had to agree, although I could sense some of the teacher’s frustrations in the words.

The point is, teaching is very public. With 30 sets of eyes on you every lesson of the week, your every word and action is likely to be noted by someone and you can be sure that it won’t be the ordinary things you do that are talked about. It will be the unusual, and mostly these will be the things you’ll wish you’d never done or said.

To the teacher at the end of her tether with a disruptive class, saying “You’re all as bad as each other so I’m giving the class detention” will have seemed perfectly reasonable. But not to the quiet, well behaved exception who is determined to keep out of trouble. And he’s the one who will tell his parents. Understandably, their position will be “you should be able to distinguish between the naughty ones and the rest”.

Like the rest of us, of course, children have a propensity for telling only half the story. So when a parent wrote about the “terrible noise and moving about in Mrs X’s lesson”, he obviously hadn’t been told that Mrs X teaches drama where some movement and noise was likely as children reconstructed battle scenes.

Children are not the only people with their eye on teachers. An employer expressed strong disapproval when a teacher supervising a work-experience placement turned up wearing an earring. “It sets a bad example,” she said, ignoring the fact that many of her workforce were similarly attired.

Visitors to the school are also quick to make judgments. A teacher sitting on a table will be thought sloppy; someone marking books while children work might be considered lazy.

At parents’ evenings, the scrutiny continues. Parents will be heard complaining that one teacher is not keeping to appointments, another “keeps contradicting herself” and a third “doesn’t seem to know my boy at all”. Comments about dress and appearance will be interspersed with complaints about unfairness and the teacher’s inability to get the best out of a particular child.

There will also be positive remarks. “My son told me what a good teacher Miss Y is,” a smiling new parent said. “Having met her I know just what he means. ”

So how does the new teacher survive in the goldfish bowl? In the main, by forgetting it’s there. If every remark or action had to be weighed in the balance of “what will this sound like when the story goes home?”, we would all be incapable of anything.

At the same time, it’s foolish to think that the classroom has the privacy of a confessional. Even when children appear to collude over some issue. “This can be just between us,” the teacher says and the children smile winningly. But it won’t be. Someone is bound to tell, and this apparent attempt at secrecy will make something innocent appear suspicious.

The best protection is a professional approach to the job. By maintaining high personal and professional standards at all times, you will be able to defend yourself against any criticism.

It’s usually when feelings and frustrations are allowed to get in the way of cool judgment that the things you wish nobody else could know about actually happen. But it also occurs when teachers become arrogant and think that being king or queen of their classroom gives them seigniorial rights.

It’s tempting to think accountability only happens through inspection, exam results or any of the other formal mechanisms. Not true. It’s going on every minute of the working day and the “inspectors” are quite as sharp as anybody the Office for Standards in Education can provide, and usually more direct and straightforward in the way they report their findings.