Make the mistake of standing near one for a nanosecond, and you'll soon hear, in mind-boggling detail, the latest batch of problems. In the words of the Swedish proverb: "Worry gives a small thing a big shadow."
A recent quick straw poll among an unrepresentative group of primary school colleagues turned up the following list of things we worry about: Ofsted, the local authority, Ofsted, funding, Ofsted, staff, Ofsted, special needs, Ofsted, disobedient children, Ofsted, and aggressive parents.
Of all of these, aggressive parents are the most worrying because at least something can be done about the rest. Parent rage seems to be growing, and never knowing when the next aggressive adult is going to burst through the door is a constant worry; although thankfully I didn't have to deal with a drunken stepdad who came to a colleague's Christmas concert accompanied by his German shepherd dog, demanding a seat, ticket or no ticket. I've not had to take a knife off an angry older brother, and I have yet to face a mother whose partner told her he had taken out a contract on her. My colleague dealt with these incidents in a way which worked for him - early retirement.
Most primary schools are not equipped to deal with disruption from angry intruders, unlike the 200 London secondary schools which belong to the Government's safer schools partnership and have their own on-site police officer. Deference is dead and we can no longer rely on the traditional respect for authority to defuse parental anger.
To get this into proportion, only 3 per cent of incidents in school involve verbal abuse or physical aggression by a parent. But even though they are rare, such actions can lead to high levels of anxiety.
For those of us who do not have our own school-based bobby, the obvious solution to serious threats of violence is to call the police, and hope for a swift response.
The Public Order Act 1986 makes it an offence to behave intentionally in such a way as to cause someone to believe that violence will be used against them, or to use threatening or insulting words or behaviour. Police have the power of arrest and this can result in a fine of up to pound;5,000 or six months in prison.
But heads are often an easily recognised member of their community. It is a big step to invoke such measures and then have to live in close contact with an angry parent who "knows where you live". Tellingly, only 4 per cent of violent school incidents are reported to the police. So worry ye not, as Frankie Howerd might have said. It's obviously not as bad as I think it is.
A comforting German proverb says: "Nothing is eaten as hot as it's cooked."
There's comforting food for thought.
Bob Aston is head of a junior school in Medway, Kent