The achievement gap between boys and girls has widened at almost all points in their education over the last three years, according to new statistics.
Assembly government figures reveal that boys' performance has worsened at key stage 2, 3 and 4 compared with their female classmates, despite a series of initiatives designed to tackle the problem.
The gender gap has vexed education policy-makers for many years, with greater numbers of girls achieving the core subject indicator (CSI) - the expected level of attainment in English, maths, science and first-language Welsh.
In the last three years, the gender gap has only narrowed slightly at KS1, with the girls' lead cut from 8.4 percentage points in 2007 to 8 points in 2009.Boys' performance at KS2, 3 and 4 improved between 2007 and 2009, but at a slower rate than girls'.
At KS2, the gap between boys and girls achieving the CSI grew from 7.9 to 9 percentage points. At KS3, it went from 8.8 to 9.5 points and at KS4 it jumped from 5 to 6.9 points.
The differences in performance between boys and girls at KS2 and KS4 are the greatest they have been for the last five years.
The knock-on effect was illustrated in another set of figures released this week, which showed that last year in Wales only 79 per cent of boys continued in full-time education after year 11, compared with 86 per cent of girls.
David Egan, professor of education at the University of Wales Institute, Cardiff, said: "What we are dealing with is not unique to Wales, but we have got to keep looking hard at this trend and what we can do to address it."
Professor Egan said a significant cause of the gender gap is low literacy levels among boys.
Estyn, the Welsh inspectorate, has made literacy a top priority in its new inspection framework being launched this September, with a particular emphasis on raising levels among boys.
An Assembly government spokeswoman said educsation minister Leighton Andrews is focused on the need for greater equality throughout the education system and is committed to raising literacy levels, especially amongst boys.
TES Cymru understands that the government is to make an announcement on a new literacy initiative in the near future, but in the meantime it is pinning its hopes for improvement on the attainment-raising School Effectiveness Framework, which will be introduced across Wales from September.
The spokeswoman said: "A key strand (of the framework) is the development of intervention and support strategies that focus on specific performance issues of which the gender gap is one."
TES Magazine, page 21.