The Assembly government is failing to tackle pupil absenteeism, according to damning criticism from the academic who authored a flagship report on addressing the problem.
Official statistics released last week show that absence rates have not improved in a decade, prompting Professor Ken Reid to describe them as the "worst" he had ever seen.
Professor Reid, who authored the groundbreaking National Behaviour and Attendance Review (NBAR) in 2008, has spoken out for the first time about his frustration at the lack of government action.
Professor Reid, former deputy vice-chancellor of Swansea Metropolitan University, told TES Cymru that questions must be asked of the Department for Children, Education, Lifelong Learning and Skills (DCELLS).
"These are the worst, most disappointing set of figures I have ever seen," he said. "This underlying trend shows there are still serious problems in our primary schools.
"It is frightening. We are not going to improve Wales's education performance until more children attend school on a regular basis. I firmly believe that if some of the NBAR strategies had been implemented we would not see figures such as these."
Official figures released last week reveal that overall absenteeism among five to 10-year-olds has increased from 6.8 per cent in 200809 to 6.9 per cent this year, while unauthorised absences have remained at 1 per cent.
The figures have shown no improvement in the last 10 years and remain higher than England, despite Assembly government pledges to tackle the problem.
Professor Reid was particularly concerned at figures showing that 48 per cent of primary pupils were absent for more than two weeks in 200910.
Professor Reid said there was an urgent need for early intervention strategies, training for teachers to manage attendance and behaviour problems, and joint approaches from health, education and social services.
"Despite all the promises that have been made, to date nothing has been forthcoming," he said. "I very much hope the government will pay particular attention to these figures and start to implement some of the recommendations as quickly as possible."
Professor Reid's comments come two months after children's commissioner Keith Towler expressed disappointment at the lack of progress on NBAR in his annual report. He said he was concerned the recommendations had "lost their way".
DCELLS officials admitted privately that NBAR was "put on the back-burner" while the attainment-raising school effectiveness framework (SEF) was being developed.
In response, education minister Leighton Andrews announced new measures last month to tackle behaviour and attendance issues, which were welcomed by teaching unions as a return of power to the classroom.
An Assembly spokesman said it was "encouraging" that attendance levels remained around the same level as the previous year despite the high number of pupils not being able to attend school due to snow.