Teenagers in care miss out on GCSEs
Nearly 60 per cent of young people in care leaving school in Wales gained no qualifications last year.
And many of the thousands of children looked after by local authorities faced unscheduled school moves - adding to the disruption to their education.
The Assembly government has still to achieve a 2003 target of three-quarters of children in care achieving at least two GCSEs. Up to March 31 this year, only 35 per cent did so - down from 37 per cent in the previous year.
A spokesperson said the government had "moved away from a single national target" and was now setting individual targets for each local authority, based on the numbers of children leaving care without qualifications.
Results had improved, with the proportion of looked-after children achieving at least one GCSE rising 11 percentage points to 46 per cent between 2000-1 and 2003-4, she added.
But teacher unions and voluntary organisations working with children said the latest provisional figures (42 per cent) were disappointing.
Geraint Davies, secretary of the NASUWT Cymru, said: "These figures should give rise to concern within local authorities and the Assembly government.
These children deserve the best possible opportunities in life, and they're not getting them."
Mike Bosley, development officer for Children in Wales, which represents voluntary organisations working with children, said the figures showed little improvement on previous years.
"The reasons are systemic. These are children who lack stability in their lives generally. They tend to have a lot of time out of school so they have a lot of catch-up to do," he said.
"They move schools, so there is a lack of continuity. And it's sometimes difficult to get the level of support and encouragement needed from carers to get them to go to school, do their homework, and go to after-school clubs."
However, some authorities are doing better than others, and most now have specialist education workers working with children in care. The Assembly government's "children first" initiative has helped fund specific programmes aimed at improving their health and educational attainment, he added.
But mental health services for young people remain underfunded, a concern raised by children's commissioner Peter Clarke in successive annual reports.
As of March 31 this year, Wales's 22 local authorities were looking after 4,431 children, and another 1,627 had been in care at some point during the previous year. Of those leaving school, 58 per cent failed to achieve a single GCSE or equivalent qualification.
In Wales as a whole, 7 per cent of school-leavers missed out on a qualification. In England, the figure was only 5 per cent.
Of the school-age children, 470 had experienced at least one change of school in the last year. The average for Wales was 15.5 per cent, but went up to 29 and 27 per cent in Denbighshire and Gwynedd respectively. Nearly a fifth of looked-after children in Denbighshire do not have an allocated social worker.
The lowest school turnover rate was in Conwy (5 per cent), followed by Neath Port Talbot and Monmouthshire (6 and 6.5 per cent). The Assembly government said setting LEAs individual targets for the achievement of looked-after children would enable closer monitoring of progress.