It’s no surprise that the Welsh Language Board wants to push the teaching of Welsh. That’s its job.

But a Straight Statistics reader in Wales wonders if it being quite fair in the way it presents the evidence. She recently received a survey from her local council on the provision of education, including material from the Welsh Language Board headed: “Welsh-medium education for your child: the best start possible”.

This makes claims about the benefits of being taught in Welsh, including the better results achieved by pupils in Welsh-medium schools: 59 per cent passes at grades A*-C in GCSE in 2000, compared to 47 per cent in English-medium schools, and 65 per cent gaining two or more A levels in Welsh-medium secondary schools, compared to 58 per cent in English-medium schools.

But these comparisons are unfair without any reference to social deprivation. In general, English-medium schools in Wales have a more disadvantaged intake, and Welsh schools take fewer socially-deprived, immigrant and special needs children.

On its website, the top item in the section in the publications on education, children and young people is a report from the Institute of Welsh Affairs, dating from 1998, that seeks to justify the claims of better performance by Welsh-medium schools. The demographic data cited show just how great the social gap is: while 12 per cent of pupils at Welsh-medium schools had free school meals, 28 per cent of those at English-medium schools did. The level of special needs at English schools was also higher, at 3 per cent versus 2 per cent.

On inspection ratings, the Welsh schools did indeed do better, but most of the benefits were organisational – better discipline, attendance, and assessment, for example. There are no statistically significant differences in achievement or learning. The gap reached statistical significance in just three subjects: English and Welsh teaching, and religious education were all better at Welsh-medium schools. The report does attempt a comparison between schools matched for intake, but in this comparison it does not include exam results, which is odd. Its conclusion is that the Welsh-medium schools are better organised and managed.

That may be so, but it hardly justifies the bold claims made by the Welsh Language Board. Nor are its claims of the benefits of bilingualism strictly honest, either. It quotes from research from Dr Ellen Bialystok of York University in Canada, (misprinted in the leaflet as Bialystak) in support of its claim that children who speak two languages “are more versatile and creative, more intellectually advanced at four to five, and better at retaining abilities into old age”.

That is indeed what Dr Bialystok claims, but she is talking about children bilingual from an early age, those who have learned two languages in the home, while the Welsh Language Board is claiming these benefits for children who only begin Welsh at school. Here is what Dr Bialystok says about that: “The overwhelming effect of bilingualism in the home is positive ... The implications for school are more complex. Children’s success in school is strongly dependent on their proficiency in the language of instruction, a relationship that holds for important linguistic abilities (eg learning to read) non-verbal computational subjects (eg mathematics) and content-based curricula (eg social studies).”

So while genuinely bilingual children may do well, sending children to a school where instruction is given in a language in which they are not fluent is a different proposition. The board also claims that 60-75 per cent of the world is bilingual, but does not make clear whether this means totally fluent in two or more languages learned from birth, or partially or fully fluent by the acquisition of a second language later.

All this made the reader who contacted me say: “The overall impression is that monoglots will not be able to work in public bodies in Wales, will achieve less and are a minority who should be ignored. Is this true or fair?”

She was also sent a flyer sponsored by the Welsh Assembly Government with a picture of a smartly-dressed toddler on the telephone. “I speak Welsh – little man, big future” reads the caption. Or, for Welsh speakers, “Dwi’n siarad Cymraeg – dyn bach dyfol mawr”. It adds: “Cymraeg – kids soak it up”. I can’t imagine it can be that easy, somehow.

There were 582,000 Welsh speakers in Wales in the 2001 Census, an increase of 2.1 per cent since 1991. It’s good news that the language is surviving – even thriving - but the board could be more scrupulous in the way it presents its advantages.