Bearing in mind the negative effects of the so-called school league tables, it is unfortunate that one has to resort to them to defend Welsh-medium schools.

Nevertheless, the headlines attracted by Professor David Reynold’s claims that the sector’s performance was worse in 20045 than 19992000 (TES Cymru, January 6) cannot go unchallenged.

His analysis is confined to just eight of Wales’s 24 dedicated Welsh-medium schools, and involves just five of our 22 local authorities. It does not deploy the national average percentage for five or more GCSEs grades A*-C as a yardstick of performance, and compares only the results of two years (199900 and 20045). Nor does he give the comparative results of neighbouring English-medium schools.

Indeed, four of the five schools showing a decline in the percentage of pupils achieving five or more good GCSE passes are situated in just one local authority.

The narrow focus of the survey makes it statistically unsound for determining the achievement of Welsh-medium secondaries within the context of GCSE results across Wales, in both the Welsh and English-language sectors.

A wider view of the attainment level of Welsh-medium secondaries can be obtained by studying the results over the whole six-year period and comparing them with the results in English-medium schools serving neighbouring catchment areas.

The main aim of this fresh study is not so much to check Professor Reynold’s survey as to test the validity of the headlines it attracted.

Wales has 24 high schools dedicated to teaching mainly through the medium of Welsh. These schools are situated in 15 of our 22 counties. As three of the 24 schools were opened after the academic year 199900, they are not included. Schools classified, somewhat loosely, as being “traditionally Welsh” are also not part of this fresh analysis.

The survey therefore comprises 21 English and 21 Welsh-medium schools.

The table (right) displays in each row the average percentage pass rate for five or more A*-C grade GCSE passes over the six-year period for one Welsh-medium school and an English-medium neighbour, together with the results for 20045.

Analysis of these results shows that for 199900 to 20045, Welsh-medium schools scored higher than their English-medium counterparts in 18 of the 21 pairs. In 20045, 17 of the Welsh-medium secondaries had better results than their English-medium counterparts, one scored the same, and the three remaining had lower percentages than their English-medium counterpart.

In Wales as a whole in 20045, 54 per cent of pupils gained five or more GCSE A*-C grades. But the percentage of pupils achieving this standard in Welsh-medium schools was consistently, considerably higher than in English-medium schools in each of the six years.

The average percentage of five or more GCSE grades A*-C for Welsh-medium schools over the six-year period was 61.3 per cent compared with 50.8 per cent for neighbouring English-medium secondaries.

Last summer’s results - 61.3 for Welsh-medium schools and 51.4 for English - puts the Welsh sector on average nearly 10 percentage points ahead.

Clearly, there is much room for improvement in the English-medium results.

Even in Professor Reynolds’ study, the Welsh-medium schools that he focused on gained better results than their English-medium counterparts with just one exception.

Welsh-medium schools cannot rest upon their laurels. But their performance is clearly a matter for celebration, not commiseration. After all, an average of 61.3 per cent of pupils achieving five or more GCSEs at grades A*- C is no mean achievement.

Owen John Thomas is the Plaid Cymru Assembly member for South Wales Central and a former deputy headteacher