We suspected that such enormous differences did not start in secondary schools. But then, data on standards in primary schools across the country did not exist.
Now, thanks to the national curriculum and associated testing, we do have detailed information about standards among 11-year-olds.
So when the data for 1995 - for nearly all the approximately 14,400 English primary schools with 11-year-olds - became available for research, I applied to the curriculum and assessment division at the DFEE. A month or two later, the information arrived and I began to analyse it, concentrating on test results for English and mathematics, both vital to secondary education.
What did the data show? First that, nationally, average standards are below expectations - by about 18 months in English and nearly two years in mathematics.
But much more striking are the very large differences in standards between schools across the country and within the same LEA. Pupils in the top quarter of schools are more than a year ahead in English and more than 18 months ahead in maths of those in the bottom quarter. And in the same LEA, pupils at the top schools are on average nearly four years ahead in English and 51Z2 years ahead in maths compared to those at the bottom.
For saying this, the TES editorial claimed that I might be genetically inclined to pessimism. But it did recognise the gravity of the situation and pointed to the need to get reading right from the earliest ages.
Others were less kind. I was rebuked for not doing something else - such as a value added analysis, when the required data were not available.
I was also castigated for not revealing the results of all the "23,000 primary schools in England and Wales". But there are only about 19,000 primary schools - the rest are secondaries - and only about 14,000, 93 per cent of which are included, have 11-year-olds.
Most criticisms are thus wide of the mark or just plain wrong. But one does have some force, although it in no way affects any comparisons of relative performance. It is that national curriculum levels are too coarse - hence the need for more sensitive measures of performance such as the standardised tests already used by many schools.
I quite agree. I spent much of 1993 arguing for this, winning the argument but losing the policy battle. And in February 1994, I upset Sir Ron Dearing and others by arguing the case publicly in an earlier report for the Social Market Foundation, Why there is no time to teach: What is wrong with the national curriculum 10-level scale.
So do read this latest report, Standards of English and Maths in Primary Schools for 1995. Better still, why not apply to the DFEE and check the data for yourself? There is much more that this - the richest database yet collected about English primary schools - can tell us.
And surely we cannot, as both Gillian Shephard and David Blunkett agree, ignore the main message - that there are severe problems in the teaching of both English and maths in very many primary schools across the country.
Parents need to know, and they need to know now, just what the differences are between schools.
So the Government should modify the arrangements for national curriculum tests to enable separate precise scores for reading and arithmetic to be produced, collected and published nationally, school by school. This would start, for primary schools, the long process of public discussion and changes in practice which have been bearing fruit in secondary schools since the Government started publishing performance tables for GCSE and A-level results in 1992.
Let us hope that we can all unite in our main goal - to enable all our children to be taught, and thus to learn, the basic skills of reading and arithmetic - the skills that are the keys they need to unlock the door to a lifetime of learning.
Dr John Marks is director of the Educational Research Trust. Standards of English and Maths in Primary Schools for 1995 can be obtained from the Social Market Foundation, 20 Queen Anne's Gate, London SW1H 9AA. The DFEE Curriculum and Assessment Division is at Room 4.10, Sanctuary Buildings, Great Smith Street, London SW1P 3BT