The progress of special educational needs pupils is not passed on as they advance through Welsh schools, according to inspection body Estyn.
Inspectors have called for a unified approach in assessing SEN pupils, claiming more must be done to monitor and evaluate their performance.
The criticism comes as a cross-party committee of Assembly members prepares to present its conclusions on the future of SEN provision in Wales. If their recommendations are accepted, they claim Wales will lead the way in helping children with disabilities succeed in school and at work.
Speaking after the release of the Estyn report, Susan Lewis, chief inspector for schools in Wales, said the success of SEN pupils should be measured by the progress made relative to an individual's "ability, age and learning context".
Inspectors recommend that the Assembly government use information on SEN pupils recorded in the schools' census and in the Lifelong Learning Wales Record, used by post-16 education providers, so that their long-term progress can be tracked in the report. They also recommend that local education authorities should consult more widely with parents, carers and pupils when evaluating educational provision.
In January 2006, 3.2 per cent of pupils in Welsh schools were under statements -legally binding documents that set out the additional teaching support needed to educate SEN children. Around pound;288 million has been budgeted for such provision in 2006-07 - an increase of 10.4 per cent on the previous year.
The committee looked into early identification and intervention of SEN pupils before investigating the use of statements.
Under a report on statements, published last May, it is proposed that only children with the severest special educational needs should be statemented.
It was concluded that professionals from a range of agencies should assess children who did not have severe or complex needs on an annual basis. The committee also suggested establishing centres of excellence for teaching SEN children within mainstream schools.