In the NHS they call them the heartsink patients; in schools, it's the troublesome parents: the angry, the indulgent, the know-it-better-than-you crowd who want all your attention just as you are getting the class settled in the morning.
And it can get worse than mere irritation. Violence in schools is on the increase. Fiona from south London is one of many teachers not ashamed to admit that they have crawled under a desk to avoid facing a potentially aggressive parent.
But most teachers face more mundane hazards in dealing with parents - that vital part of the job for which they have received no training.
Protectiveness can be a powerful drive - and frustration acts as a motor. As Romey Tacon, head of Peacehaven infants school in Brighton, says:
"Parents get upset because they are anxious. Some parents may feel disempowered, and school can be the main interface with a society they feel rejected by."
There are, she concedes, some parents you will never get on your side, just as there are some children whom it is hard to reach, but "you have to keep listening," she says.
It is important, agrees Mike Beale, head of Holland Moor primary school in Skelmersdale, "not to rise to provocation". In 16 years of running a school in an area of high social deprivation, Mr Beale has never had a major problem with parents. He also puts success down to strong relationships with the community. "Parents are our partners," he says.
Regular newsletters from school and from class and high visibility of staff before and after school are part of the recipe. Most important, he insists that every teacher each day finds the parents of one or two children after school and tells them of something good their child did.
It's the kind of attitude which would have made all the difference to Joanna, a parent in west London who felt that her child's special educational needs were persistently neglected. "They never listened, they never answered our concerns."
For Peter Gordon, head of Hazelwood infants in North London, listening is the key. But, he warns, "draw back a bit, too". Otherwise you can be overwhelmed by people such as the parent who threatened to take a school to the European Court of Human Rights if they did not get the children to make cards for Fathers' Day as well as Mothers' Day. Or the abusive parent who ignored a restraining order because "I am French. English law doesn't affect me."
So if there is a Golden Rule, it is to listen, and with respect. But as Mr Gordon, with an MA in home-school relations and years of running parent-school workshops says, "People will always surprise you."
* THE ABUSIVE PARENT
It's no surprise when Mr Angry visits. Little Johnny Angry and Jenny Angry are famous for their tantrums, low achievement, frequent spells outside the head's office and disruptive behaviour.
It probably only takes a note home explaining that Johnny has been excluded during lunch hours this week for Mr Angry to thunder into the office or waylay the teacher outside the school gates.
As the Angry family are not averse to physical violence, don't get involved in a fight, verbal or otherwise.
NEVER SAY: "Well, I can certainly see where he gets it from."
AVOID- Threats. Angries thrive on menace.
BEST TACTIC: Sympathise. "It is really difficult, isn't it? I'm sure you understand how we want to be fair to everyone." Be very straight. Offer to meet with the whole family after school, to help with school work.
UNDERSTAND: Angries feel perpetually belittled. Explain that any disciplinary measures are not about punishing but about making a safe environment for everyone. This includes their child. Do they have any suggestions themselves?
* THE PARENT WITH A GRIEVANCE
Hangs around. A lot. Is pursuing the grievance endlessly, via councillors, MPs, the various branches of the LEA, other parents at the school gate, the PTA and possibly the local press.
Needs to talk about it a lot, as well. Is very fluent on the grievance, but seems to have little else in his (or her, but probably his) life. Likes to "keep you posted" with sheafs of paper. Primes the pupil with details of the grievance which, unfortunately, the pupil often uses as a reason not to do his or her work.
Beware - this could be seen as not accessing the curriculum and feed into the grievance.
NEVER SAY: "Get a life."
AVOID- Reading the documents. At this stage, your opinion will make no difference.
BEST TACTIC: Concentrate on the child and do your best for whatever difficulty he or she is experiencing. It may well be true that local authority help, for instance, is not all it should be, but professionally, you can only point this out and get on with your own job.
Try to involve the parent governor. It may be that a social response is the best. Also, governors can help in dealing with the local authority.
UNDERSTAND: It is very painful when a child has a problem in school, where they should be safe and helped to thrive. Listen, but not beyond the point when you start to feel resentful. Try to focus on the practical, not on the underlying emotion, which can suck you in.
LAST RESORT: Set limits on when you will speak to the parent: for example, a regular Tuesday for 10 minutes but no more.
* THE INARTICULATE PARENT
Scarcely comes to school. May not be able to read or write well - or at all. So may never have had any communication from the school. Distrusts school - "What did it ever do for me?"
Never asks about child's day, never encourages homework. Has been seen to tear up artwork lovingly and joyfully presented with a casually brutal:
"Another load of rubbish again."
Mrs Inarticulate would prefer to keep the children at home where they could help out but is scared of the law. Later, when her kids reach the mid-teens, they will probably not attend.
NEVER SAY: "Do you want them to end up like you?" AVOID- Putting the Inarticulates on the spot and exposing their ignorance.
BEST TACTIC: Praise the child. Both in class and whenever you meet the parent. Make it clear that the school values every pupil, and that each has uniquely wonderful qualities.
Ask about the parents' school experience and invite them in, to see how things have changed - for the better.
UNDERSTAND: Aggression is a defence. It's an information-laden world and the Inarticulates sense this. They would like to be involved but no one has taken the time to let them in.
LAST RESORT: Homework clubs as a safe place to concentrate.
* THE TEACHER PARENT
Probably only seen at parents' evenings but then likely to take up about three times as much time as anyone else discussing the national curriculum, and whether the literacy hour is eating into creative writing. All very interesting, but you can see the queue getting restless.
Anyhow, all this stuff is just so much snow. What Mrs Teacher really wants to know is why Melanie is not well above the class average as, no doubt, a child of her ability would be in Mrs Teacher's own school.
And why didn't you mark her homework last week? And she seems to have been reading the same book for a long time.
NEVER SAY: "Why don't you send her there then?" AVOID- Getting drawn into comparison. Sure, you could go on about the different profiles of the schools, but it won't make any difference - and the queue will just get longer.
BEST TACTIC: Ask advice. "I wonder how you think we could best motivate Melanie to achieve her potential?" UNDERSTAND: There is a lot invested in education in this family. Mrs Teacher needs her child to do well. And remember, she could be you. It's better that she talks to you now than that she broods and enlarges her worries to herself and others in the playground.
LAST RESORT: Suggest swapping classes for the day. "Then we could really understand each other's positions."
* THE INDULGENT PARENT
It's always someone else's fault, isn't it? Jamie Indulgent literally can do no wrong, says his mother.
Other people, somehow, don't understand this and say he does not share, he kicks, and shows off all the time. But they are wrong. After all, when you give someone everything they want, it must make them and everyone round them happy. (Why this is not so is one of those great mysteries of human life, but one which most of us have worked out by the time we reach 20. Not Mrs Indulgent, though.) And, anyhow, "he's not like that at home."
NEVER SAY: "Have you ever thought of giving him a good clip round the ear?" AVOID- Pointless arguments about who said what to whom in yet another playground dispute which Mrs Indulgent has come in to complain about.
Simply say, "We can't really know what happened. But what do you think we should do now?" BEST TACTIC: This parent is the one with whom a home-school agreement might work. It will take a lot of work, but regular logging of incidents and a calm approach could do the trick.
Another one where other parents, like the parent governor, might get involved. Perhaps even helping in class, so Mrs I can see what goes on for herself.
UNDERSTAND: Parents spoil because they feel guilty for not giving enough attention. Children play on this. Reassurance that the child is being properly cared for should disarm some of these feelings.
LAST RESORT: Video child to show obnoxious behaviour.