Thousands of children have been examined every 10 years since 1973.
A third of children in Wales were said to have good oral health overall, which compares to 39% in England.
Decay was found in 52% of 12 year olds and 63% of 15 year olds, a slight improvement on the 2003 survey.
But around 70% of them reported problems with their teeth.
Decay was found in 41% of five-year-old children in their primary teeth and in 55% of eight-year-old pupils, according to the Health and Social Care Information Centre report.
Severe dental problems were worse among children from poorer backgrounds.
Around a half (47%) of five year olds could be said to have good oral health.
But that declined with age, to around a quarter of 15 year old children.
Other findings:
The last results in 2003 showed that oral health had improved greatly since the 1970s and 1980s.
This time, 12 and 15-year-olds were also asked to fill in a questionnaire on how they looked after their teeth.
In 2009 the Welsh government launched a national scheme to encourage better dental health amongst young children. Since then it has invested over Â£12m in the programme.
It also suggested the programme had led to a recent  6% drop in the proportion of five-year-olds experiencing dental decay.
Experts point out there could be several reason the health of children's teeth in Wales was still lagging behind those from other UK nations including socio-economic conditions.
That survey 10 years ago also showed a big drop in 15-year-olds with obvious decay from 94% in 1983 to 58%.
Scottish children are not included in the 2013 survey but Wales has better results than Northern Ireland, where 31% were judged to be in good oral health.
The Welsh Government said its own most recent monitoring survey showed a 6% drop in the proportion of five-year-olds with dental decay.
"However, there is more to do to improve the dental health of children in Wales especially since the vast majority of tooth decay is avoidable," said a spokesperson.
"Parents can help their children by reducing sugar intake and encouraging them to brush their teeth twice a day with fluoride toothpaste. "
It has also published its own survey of dental health to identify how much decay among five-years-olds is already present at the age of three.

Chapman's Ice Cream initially offered to purchase Beavercrest Community School in Markdale for about CA$1m ($741,000; Â£596,000).
"This is the community that helped build us to what we are," vice-president Ashley Chapman told the BBC.
Although regulations and an asbestos problem might make buying the school difficult, he said the company will work with the school board to come up with a solution that works, and intends to help cover some costs.
"Somebody's got to step to the plate and somebody's got to help fix the situation," he said.
Mr Chapman proposed buying the building and leasing it back to the school board at a reasonable rate in order to keep the school open.
But the aging building could require millions of dollars worth of repairs, and regulations make it tricky for a private company to buy a public building still intended for public use.
"Essentially what we were proposing was a giant band aid to delay the situation," he said.
The school is one of about 600 - many in rural areas - that the province has earmarked to be shut down in order to save costs.
If Beavercrest were to close, children from the town would have to spend up to 90 minutes in a bus commuting to one of three other schools in the area. It has 195 students but has a capacity for 319, according to a recent report by the local school board.
"We all realise that something needs to happen and something needs to change, but whatever happens needs to benefit the students," he said.
An alumnus of Beavercrest himself, Mr Chapman said helping isn't just the right thing to do, it's smart business.
Chapman's, which was founded in 1973 by his parents, is one of the largest ice cream manufacturers in Canada and has doubled its workforce over the past six years, he said.
The company intends to expand even more, and that means they need to attract people to the small town of Markdale, which has a population of just 1,325.
Mr Chapman said he's already struggled to attract people to the area, even after raising wages.
"Where are these people going to come from, especially if we don't have an elementary school in this area?" he said.
Only a third of children in Wales have healthy teeth overall and this is lagging behind England, a major survey suggests.
[NEXT_CONCEPT]
A Canadian ice cream manufacturer hopes it can give something back to its local community, by keeping an elementary school in Ontario province from shutting down.