By Gary Eason
Education editor, BBC News website
The proportion of 11-year-old boys able to read, write and do maths to expected standards in England went down this year, latest figures reveal.
The trend in results over recent years
Last year 52% achieved expected Level 4 in their national curriculum tests. This year's provisional figure was 51%.
The government - which has previously prioritised boys' performance - said it remained absolutely committed to improving boys' education.
Tories say the data shows ministers are not "getting the basics right".
The government published the results as part of a series showing a general improvement since 1997.
The statistics were put onto the Department for Education and Skills website on Friday as an amendment to earlier figures on the overall performance of boys and girls together.
Those showed 57% attaining the expected level, the same as in 2004.
The department's head of statistics took the decision to publish those, on 12 October, "in response to recent media interest".
Unusually, a note on them referred to the prime minister's monthly press conference the previous day.
It said Tony Blair had confirmed that the proportion of pupils achieving Level 4 in reading, writing and maths tests in 1997 - when Labour took over government from the Conservatives - had been 43%.
What was not given at the time was the gender breakdown.
That has now been produced and shows that 51% of boys achieved Level 4 in "the three Rs".
The figure for girls was 63% - up one point on last year and enough to keep the combined total the same as last year.
The initial impression when this year's results were issued in August had been one of improvement, with two percentage points more of boys reaching the expected level in English as a whole and a similar rise in maths.
But those initial figures do not give the overlap - the percentage of boys getting both English and maths.
And on the particular indicator of reading, writing and maths which the department has chosen to publish, it can now be seen that the performance of boys got worse.
A spokesman for the Department for Education and Skills said: "Standards in English and maths are at their highest levels ever.
"Currently 70% of children achieve Level 4 in both subjects, compared with only 52% in 1997.
"In 1997 just 38% of boys reached this standard, this has now improved to 51%.
"While we are working hard to close the achievement gap between boys and girls, the fact remains that record numbers of boys and girls are reaching or exceeding the expected standard for their age."
Shadow education secretary David Cameron said: "Once again, the government have been caught out being less than frank with education statistics.
"The combined figures for the 'three Rs' at age 11 were only released after Conservatives published a leaked email from the education department showing they had been suppressed.
"Now it seems that even the figures they published following that row were not the full picture.
"If we are to have a grown-up debate on getting the basics right in our schools, ministers must stop playing fast and loose with the facts."