If you want to take the temperature of the nation, hang out in its staffrooms. Teachers work at the sharp end. They see what’s going on, hear what people are saying. From watching their pupils, they see where it might all be heading.

At the start of 2005, for example, I visited a garden city in the South-east - a well-grassed place with roundabouts, bike paths and quiet estates full of tidy cul-de-sacs. But teachers at the primary school I visited were keen to point out that things were not all they seemed.

Unemployment was high, young families struggled, and drug problems were endemic. Drug problems? Here? “You bet,” they said. “And we’re not talking about kids, either,” one teacher said. “We’re talking about adults in their 30s and 40s. Off their heads every weekend. Spending a fortune. They think it’s normal. Do people have any idea how much drugs are wrecking ordinary sorts of places like this?”

Well, no, they don’t. Not unless they are teachers, or the Joseph Rowntree Foundation, which some months after this school visit published a survey on drug use saying exactly what these primary teachers could have told them for nothing. If anyone had thought to ask.

Then it was on to an inner-London secondary where pupils came from a dozen main ethnic groups, each of which teachers said was performing quite differently. One group was strong at maths, another at art and dance. There was a group that struggled with English but had supportive parents who kept them at it. In yet another, frustratingly the children were very able but mainly left to fend for themselves, so they often fell out of school into a life of crime... On and on it went - the nuances, the carefully calibrated differences, not at all politically correct but rich in wisdom about the local community and the differing needs of the children within it. These teachers had their fingers tight to the pulse of complex and shifting ethnic realities, while most of us on the outside are left using crude newspaper headlines about how Asian and black pupils are doing in school to colour in the racial map.

Then there was the private girls’ day school, where the head was worried about the slavish devotion of wealthy parents to their children’s every whim. “How are these girls ever going to fend for themselves?” she fretted, “when they’re growing up like jelly because they never have to struggle to develop their bones.” And the PE teacher at a Midlands school who said that, if anyone had asked her, she could have told them 10 years ago that we were heading for a national epidemic of obesity just from the dwindling number of pupils who could run 50 yards without gasping for breath.

Teachers know what they know because everyone has to put their children through school - whether they are sick or well, rich or poor, honest or crooked. Schools deal with society across the board, and know what is going on in it. Teachers know that children are more restless and volatile than they were, and that more youngsters are succumbing to eating disorders and self-harm.

They know what family break-up can mean for children, and how an economic recession will often show up early at school in cancelled music lessons and under-subscribed holiday trips before anyone else realises what is going on. So my biggest educational wish for 2006 is that teachers will increasingly stand up and tell us what is happening in our world, and what they think should be done about it.

Why do we need Jamie Oliver to point out that school dinners are rubbish when teachers have known this for years? Why pay for expensive educational research to tell us that poverty and low achievement go hand in hand when it’s blindingly obvious to anyone who works in a school?

At present, the teachers’ public voice is confined to a low-level whinge about working conditions that reaches a crescendo every Easter. This needs to change. Teachers should make a resolution to speak out at every opportunity, knowing that what they see is important, and that their views on it matter. They know a lot that we don’t, and this knowledge is much too vital to be kept behind the staffroom door.

Hilary Wilce writes an advice column for parents in The Independent