As you gaze out at the smiling, snarling or blank faces of your new class, imagine they are the tip of an iceberg of psychosocial factors. Beneath the water lies a mass of varying family histories that will have produced a myriad of emotional states and behavioural quirks.
But there are different patterns to the kind of family histories experienced, comparing different societies and different times. To put it another way, patterns of childcare in a community profoundly affect what sort of children turn up in your class. This can work for and against harmony and scholarship.
For instance, in 1979, just under a fifth of children were being raised in a low-income home; by 1981 it was nearly one in three and has stayed near that mark ever since. Violence is caused primarily by being young, male and from a low-income home when young. Sure enough, after 1987, as Thatcher's infants and toddlers grew into boys and teenagers, rates of violence accelerated at an unprecedented rate - more boys being raised by stressed-out, low-income parents led to more violence, including in the playground.
A more recent trend is towards placing under-threes in daycare. A mass of evidence suggests that, while many children do not suffer as a result, many others do: more insecure, more disobedient and more aggressive. It follows that if more children are placed in daycare during their first three years, primary school classes will be more disrupted. Jay Belsky, the distinguished American developmentalist now working in the UK, has tested this hypothesis.
Using a sample of 3,440 children in the kindergartens of 282 American primary schools, Belsky and colleagues explored whether increased numbers of children who had been in daycare in the early years affected classroom behaviour as a whole. The findings are highly significant, especially when you recall this government's support for group daycare in its SureStart schemes.
First of all, the higher the proportion of children who had been exposed to non-parental care of any kind, not just group daycare, the more disobedient and aggressive the class. The effect was even more pronounced if the proportion who had been in group daycare was higher. Most dramatic of all, the effect was not only on children who had had substitute care, it was also on children who had not.
Children who had only parental care were more aggressive and disobedient if they were in classes with many who had not, especially if it had been group daycare. In other words, if your class has a high proportion of children who spent a lot of their early years in group daycare, the remaining ones who were raised at home by parents are likely to become more disobedient and aggressive too.
Prior research had already established what every teacher knows - that the more seriously disturbed children with behaviour problems there are in a classroom, the more unmanageable the class as a whole. A new American study of a large sample of primary school pupils demonstrates the classroom effects of having children who have witnessed domestic violence.
The authors estimate that for every one extra troubled peer in a classroom of 20 pupils, the number of disciplinary infractions rises by 16 per cent. The authors estimate that, overall, in American primary schools, pupils having witnessed domestic violence increases disciplinary infractions by 48 per cent (compared with if none had done so).
Unfortunately, it is not an option for you as a teacher to start the new school year by asking your primary school pupils to raise their hand if they have been in group daycare or witnessed domestic violence - although if you could, it would give you a clue as to what lies in store. However, it's not all bad news: the answer to the question might also predict better exam results as well.
A composite academic measure (reading, maths and general knowledge) in Belsky's study showed that children who had been in daycare scored slightly higher than those cared for exclusively by parents. What was more, children only cared for by parents who were in classes with lots of children who had been in day care did better than those in classes with few children who had been in daycare.
So if bad behaviour caused by non-parental care is contagious, so is enhanced academic performance - at least at the start of school. As your temper reaches breaking point, you can console yourself with the thought that this could be the price of better Sats results in your class
Oliver James is a child clinical psychologist and the author of They F*** You Up: How to survive family life and Affluenza. His new book is Contented Dementia: 24-hour wraparound care for lifelong well-being.
James, O.W. Juvenile Violence in a Winner-Loser Culture: Socio-economic and familial origins of the rise of violence against the person (Free Association Books, 1995)
Dmitrieva, J., Steinberg, L. amp; Belsky, J. (2007) Child-care History, Classroom Composition and Children's Functioning in Kindergarten, Psychological Science, 18:12, 1032-9
Carrell, S.E. amp; Hoekstra, M.L. "Externalities in the Classroom: How children exposed to domestic violence affect everyone's kids" (August 2008). NBER Working Paper No. 1
Available at SSRN: http:ssrn.comabstract=1231694.