Every black man has a police story, a school story, and a job story.

As the row continues over whether the Metropolitan Police Service is institutionally racist or not, the police stories have bubbled and flowed across the airwaves and phone lines. Being stopped late at night in north London is no surprise - we know that police are up to eight times as likely to stop and search a black person as a white one.

When it happened to me, having completed a breathalyser test (showing zero alcohol intake), shown my driving licence and insurance documents to Copper Number One , I heard Copper Number Two calling in my licence plate number and personal details - evidently to check that I had not stolen my own car.

The full horror of what was going on dawned only when I heard the disbelieving tone in which the words “IC3”( police code for Afro-Caribbean) and “Jaguar XJ6” were put together in the same sentence. Evidently part of the acquired experience of this particular police force is to suspect black men who appear to be too affluent.

Today I drive a less ostentatious vehicle. It’s the sort of tiny compromise that most black people adopt to avoid continuous conflict. But the problem lies with institutions rather than people.

The great significance of the Stephen Lawrence case lies less in the particulars of police behaviour, and more in the fact that Doreen and Neville Lawrence have received sackfuls of sympathetic mail from families who see them purely as fellow human beings rather than as political symbols. The people have moved on where the police service has not.

That said, both of the police officers in my story would probably be genuinely astonished to be told that their actions were racist. That’s because they confuse biased actions with allegations that they have a campaign of persecuting blacks. Few believe that the police or schools are staffed by people who hate ethnic minorities. The real worry is that the way these services work, irrespective of the personal views of the individuals inside them, produces an outcome which is biased.

The very first story I ever did as a television journalist concerned a trade union official called Percy, who effectively ran the refuse service in an inner London borough. Then, most recruitment took place (as in the docks and the fire service) through word of mouth; jobs were handed down to sons and nephews and friends. The justification was that this would produce a more cohesive group in a difficult workplace; “outsiders” would feel uncomfortable.

Percy argued long and hard that letting in people who did not know “the dust” would compromise the quality of service. The result of the policy was obvious: a service which was all-white remained so in spite of the change in the local population. As recently as last year, breakaway trades unionists at Ford’s Dagenham plant made the same case for keeping the recruitment of lorry drivers in the hands of the union officials. Yet some of these men would gladly stand up for anti-racist causes, and, in the case of the car workers, even elect a black general secretary.

Teachers have their own case to answer: why is the practice of exclusion so heavily biased against black boys? This particular bias is simply too widespread to be put down to “a few bad apples”. Is there a massive hidden hatred of black children lurking in the nation’s staff rooms? Unlikely, unless I happen to know the hundred or so least typical teachers in the country. What is far more likely is that a combination of two things is skewing teachers’ behaviour.

First, there is the accreted wisdom of a couple of generations which says that black boys are boisterousnot academicalienatedsometimes aggressive. No matter what a teacher believes personally, and no matter what their real experience is, even the most race-aware teacher will have this background noise floating in his or her mind. Everything which reinforces the image is noted as routine; everything which undermines it is noted as a pleasant, surprising exception.

The other kind of factor which produces bias is structural. In the police case, one of their great yawning gaps is the absence of black officers - the Met polices an area where one in five of its citizens are people of colour; among its own staff, just over one in 50 is non-white. This is partly accounted for by historical barriers - famously, for many years, the height requirement (which in these days of martial arts training seems to have little real practical value) worked to the disadvantage of some Asian communities.

In schools, we might need to take another look at the true impact of school league tables, parental choice and local management of schools. Is it true, as many black parents are beginning to suspect, that one reason their children are excluded is to avoid depressing exam results?

Worse still, is there any validity to the complaint that one black headteacher recently made to me that the schools which are being placed on the Department for Education and Employment’s target list for closure are the ones that white parents feel reluctant to send their children to, because the majority of pupils are black?

These all seem to me questions to which both the National Audit Office and HMI might usefully address themselves.

We need to know where the bias is occurring and ensure that we aim our righteous anger at the correct targets; it’s too easy to blame individuals.

When Benjamin Franklin first used the phrase “one bad apple” his point was that they “spoil their companions”.

At the moment we live in a Britain where a series of individual decisions, all perfectly innocuous in themselves, have created a mountain of racial bias. It’s no one’s fault - but it’s everybody’s responsibility.

Trevor Phillips is a broadcaster and journalist