Attendance and attainment among Gypsy and Traveller pupils in secondary schools remains too low, despite the best efforts of dedicated education service staff, according to Estyn.
In a report, the Welsh inspectorate says that despite improvement in some local authorities, progress on improving attendance and attainment levels has been too slow.
There are also marked inconsistencies across local authorities in quality of provision. The Welsh Government has set up a nationwide group to share good practice, but Estyn says its work has not had a big impact.
The Government's minimum attendance target for Gypsy and Traveller pupils is 50 per cent, but many still fall below that level.
Attainment among pupils at key stage 3 who identify their ethnicity as Travellers of Irish and GypsyRoma heritage is also extremely low and has fallen further in recent years. At KS4, no gypsy or traveller pupils achieved the core subject indicator.
However, Estyn found that it was difficult to gauge the true extent of the problem as data collected is not always accurate.
Chief inspector Ann Keane said: "The challenge for schools and local authorities is to keep on building their relationship with the travelling community in order to create more positive attitudes among parents. We know that attendance and attainment rates are highly dependent on the value that families place on formal education.
"Secondly, more schools need to develop a curriculum that actively promotes the Gypsy Traveller culture and adopt policies and practices that meet the needs of Gypsy Traveller pupils and their parents."
The Welsh Government welcomed the report and said it has started to implement some of the recommendations on funding and data.
A spokesman admitted the slow progress on attendance was "disappointing", but said the grant to local authorities for the education of Gypsy and Traveller children will be increased by over 22 per cent by 201314.
"We are committed to providing education for all children and young people in Wales regardless of their background," the spokesman said.
"The often interrupted nature of their school attendance, and beliefs within the community, however, means that mainstream schools may not offer the only appropriate form of education for this challenging learner group. We will be exploring this further."