The schools watchdog in England, the Office for Standards in Education (Ofsted), studied 211 schools which have been running schemes similar to the national numeracy strategy. In some "weak" schools there were "substantial improvements", it says - but in some, maths performance actually declined.

The Education Secretary, David Blunkett, repeated only last week that his head was "on the block" over numeracy targets.

The scheme has helped boys do better

He has promised that by the next election, 75% of 11-year-olds will achieve the standard of numeracy expected for their age. This requires an improvement of 5% a year in the national average. But this year, results worsened.

The national strategy stresses traditional maths teaching, including mental arithmetic and times tables. A daily "numeracy hour" is to be introduced this autumn, similar to the literacy hour which began this academic year.

Weak leadership

Ofsted's report on the pilot says: "The variations in year-on-year improvement, which are likely to be replicated in many schools in the country as a whole, indicate that progress towards the standards target will be neither even nor straightforward."

There was considerable progress, with 11-year-olds up to 16 months ahead of similar children after two years of the new methods. But Ofsted identifies an "unacceptable gap" between the best and worst schools.

Recruited: Pupils at a London school trying out maths teaching software

"If the gap between these schools and those in more favoured circumstances is to be closed, teaching of the highest calibre will need to be sustained," Ofsted says.

The key factor, it says, is that in almost a tenth of schools "deep-seated weaknesses in leadership, management and the quality of teaching combine to reduce the impact of the project."

But a high turnover of teaching staff and recruitment difficulties are problems in disadvantaged areas. Only a few days ago, the Liberal Democrats warned that cash bonuses of up to £5,000 for new student teachers was failing to attract more recruits for subjects that have a shortage, such as maths and physics.

Generally doing well

Even so, Ofsted makes it clear that the numeracy project has, overall, been a significant success. Support and training courses did produce what it regards as a significant improvement in the quality of teaching.

• pupils made significantly better progress in both mental and written numeracy tests than would have been expected
• the project helped to close the attainment gap between all ethnic minority groups and white pupils
• the proportion of satisfactory or better teaching rose from 70% to nearly 80% of lessons between autumn 1997 and last summer
• the numeracy hour helped to increase pupils' motivation and concentration and led to an improvement in behaviour.

Ofsted inspectors made three visits to a sample of about 40 of those schools - the first shortly before the schools started the project. The follow-up visits, in which 248 numeracy lessons were observed, were used to evaluate the improvement in the quality of teaching.