Opposition parties attacked the Assembly government this week after new figures revealed a rise in 2004-5. However, education unions claim the increase could be down to one thing - a cheap package holiday in the sun.
Overall, absenteeism in Welsh primary schools was up from 6.8 per cent in 2003-4 to 6.9 per cent last year. Unauthorised absenteeism increased from 0.7 to 0.8 per cent. And it was also higher in areas where a greater proportion of pupils were entitled to free school meals (FSMs). In areas with 32 per cent or more of children receiving FSMs absenteeism was 9.1 per cent, compared with 5.2 per cent in areas with just 8 per cent or below.
Conservative education spokesman William Graham said the government was failing to get to the root cause of absenteeism, despite schemes such as free school breakfasts.
But Dr Heledd Hayes, education officer for the National Union of Teachers Cymru, said members had also noticed more children were going on holidays during term time.
She said: "Parents who believe their child is going to get an education from a package holiday in the Costa Brava are mistaken - a week means a lot of catching up."
A review by the education welfare service (EWS), due out in April, is expected to recommend ways to improve attendance.
Parenting orders and contracts also mean parents can be prosecuted for taking their children out of school during term time.
An Assembly spokesperson said: "We must look at the underlying problems which lead to truancy by making our schools a positive place for learning which our young people want to attend."