Less than 10% of primary schools in Wales are offering their pupils a free breakfast, a year after the scheme was introduced by the assembly government.
The breakfast scheme offers pupils cereals, fruit and juices.
Figures show 148 out of a possible 1,588 primaries will offer their pupils a free breakfast by the end of the autumn term.
An assembly spokesperson said the scheme was a pilot and part of a "three year rollout" across local authorities.
Opposition parties in the assembly have criticised the initiative.
The free breakfasts offer was a key pledge in Labour's 2003 assembly election manifesto.
Education Minister Jane Davidson said she introduced the breakfasts in response to evidence that some children were being sent to school hungry, which can affect their work and behaviour.
The current estimated cost is £10m, based on the assumption that 80% of primaries will take part and, of those, 30% of their children will have a free breakfast at school.
Ms Davidson said: "There's huge support for the initiative from the schools that are participating. We know from them that children are coming in earlier, they are more punctual therefore for lessons, their attendance is better.
"And of course, a particular initiative in this scheme is that we're demonstrating what a healthy breakfast looks like, because were only providing healthy breakfasts through this scheme.
"It's really important that people take up this opportunity to ensure that their children are best prepared for the school day."
Jane Davidson said breakfast helped pupils to be 'best prepared'
The scheme began in some of the most deprived parts of Wales.
Around two-thirds of children at Goetre primary school on the Gurnos estate in Merthyr Tydfil are also entitled to free school lunches.
Head teacher John Bibby said up to 100 of the 202 pupils in the school during the summer had taken advantage of the free cereal, fruit and juices. Second helpings were available for 5p or 10p.
He said: "For our school, it has had a profound effect. The children aren't hungry during the school day because they have access to a full, healthy breakfast.
"It has been such an asset to the school that even if the funding was withdrawn, we would find some funding for a breakfast club."
Conservatives said children were better off having breakfast at home with their families.
Tory AM William Graham said: "This is not a moment to celebrate. Free school breakfasts have been exposed as a sham.
"Labour's pre-election gimmick was nothing more than an uncosted con designed to win cheap headlines and deceive parents and children across Wales.
"It is abundantly clear that the assembly government has been making it up on the back of a cereal packet as it goes along."
Liberal Democrat AM Peter Black said: "The school breakfast initiative, although quite useful, it's going to cost a huge amount of money which might be better spent (if) the schools themselves had the choice of using that money."
Plaid Cymru AM Janet Ryder said the breakfast scheme was not reaching the children who needed it most. She said pilot studies had shown only one school had more than a 50% take up.
She said: "The ones who are using this scheme are the ones whose parents know that they can have free pre-school care for their child."