This January, some 620,450 secondary pupils were seen by their schools as having special educational needs below the level where a statement was issued. This equates to nearly one in five of all pupils. Add those pupils with statements, and the incidence rises to more than one in five of all pupils in secondary schools.

There are more pupils with special needs in primary schools: some 742,000 of them are without statements, and nearly 58,000 have a statement. However, their incidence is 19.6 per cent, which is slightly less than in the secondary sector, possibly because some needs only become identified as pupils progress through the school system.

But this still means that in any average primary class of 30 pupils, six will have a degree of special needs. In some areas, these pupils will be in addition to those who struggle with English as a second language and others who have joined the school part way through the year.

Of course, not all schools are average, and some will have a higher incidence of pupils with special needs, let alone those with other needs. In a few cases, the overall percentage could be more than one in three pupils in any classroom. Add in the other challenges of language and pupils changing school, and the success of many schools comes into a sharper focus.

Perhaps the bonus for teaching in a challenging school should apply equally to primaries and secondaries since first-class teachers are needed equally in both sectors. But that, at least as far as primaries are concerned, was something noted more than 40 years ago in the Children and Their Primary Schools report by Lady Plowden.

John Howson is a director of Education Data Surveys, part of TSL Education.