Five years after the target of two hours a week of physical education for all pupils was set, only a third of primary schools are delivering it, the schools inspectorate told MSPs this week.
Of 237 primaries inspected last year, only a third were offering two hours of PE per week at each stage, the health and sport committee's sports inquiry was told by HMIE inspector Donald MacLeod.
Secondary inspections showed an improvement - some two-thirds of schools met the target at S1-2 and a majority at S3-4. However, at S5-6, only one in seven schools did so.
The main barriers were a lack of trained staff and poor facilities, particularly in primary, said Bruce Robertson, director of education in Aberdeenshire and a past president of the Association of Directors of Education in Scotland.
Although authorities had maintained numbers of PE staff, none had been able to increase them, a survey of authorities showed.
Since training provision in PE for primary teachers was restricted to Glasgow and Edinburgh, authorities outwith the central belt faced an additional barrier.
Mr Robertson made a plea for greater flexibility. A number of secondaries operated periods of 55 minutes rather than a full hour, for example, and they were not counted as meeting the target. And the two hours should include the broader concept of physical activity, rather than the more restricted notion of formal PE.
He said a broader view should be taken of primary schools' provision of physical activity, particularly as the health and well-being strand ran through all areas of A Curriculum for Excellence. Outdoor education should be included in calculations reflecting pupils' physical activity levels, he added.
"Two hours of poor PE is no benefit, particularly to some teenage girls who would rather have two hours of exciting physical activity delivered in exciting ways," Mr Robertson argued.
Rodney Stone, chair of Vocal, the professional body representing local authorities' chief officers with responsibility for culture and sport, told the committee that children should be doing a minimum of 30 minutes to an hour's physical activity per day, four times a week - "the kind of activity that gets you a bit out of puff". But, he added, "we need to look beyond what can be provided within the curriculum".
MSPs, however, said their experiences on the ground did not reflect local authorities' findings.
The SNP's Ian McKee, a Lothians MSP, described his visit to an unnamed primary school where the head had spent all the specialist budget on art instead of PE.
Lib Dem Ross Finnie and Labour's Jackie Baillie, both from the west of Scotland, said PE teachers in one secondary school told them that the physical literacy levels of S1 pupils were at their lowest levels for several years.
Mr Robertson responded by saying that authorities had been given no money to deliver the PE target, only ring-fenced money for training teachers to deliver PE. In Aberdeenshire's case, that had been Pounds 18,000.
Meanwhile, a separate review of physical activity has reported that nobody knows how much physical activity people in Scotland are doing - six years after publication of a landmark document designed to boost exercise levels.
Although there were a number of encouraging projects around the country, with schools in particular making notable strides forward, their impact remained "relatively unknown", the report found.
The review looked at progress since the publication in 2003 of Let's Make Scotland More Active. John Beattie, chairman of the National Physical Activity Strategy Review Group, told The TESS he was "a bit disappointed - five years ago, I thought we would be further ahead".