There is too much focus on slavery and colonialism in teaching resources about black, Asian and minority ethnic (BAME) themes, according to a new report.
A working group, established by the Welsh Government, found "major gaps" in resources to support the teaching of BAME themes across the curriculum.
It said health and well-being, maths, and science and technology were particularly lacking.
The Welsh Government said it would consider the recommendations in detail.
The group, chaired by Charlotte Williams from Bangor University, was established in July to look at how the contributions of BAME communities would be reflected in the new curriculum being rolled out from 2022.
Its interim report focuses on the resources currently available to support teaching, ahead of a final report which will assess the training and support needed by teachers.
The report calls for a change to "the narrative around the teaching of black, Asian and minority ethnic themes", and for the emphasis on issues such as slavery and colonialism to be balanced by resources focused on "the wider histories of black, Asian and minority ethnic communities in Wales".
It said focusing only on negative events in history could lead to BAME children having a negative sense of themselves.
A review of Hwb - the Welsh Government's database of teaching resources - identified only 11 resources with a black history focus. The majority were "outdated, lacking in supporting material for teachers, and of little relevance to Wales".
The group also raised concerns about the quality of translations in Welsh.
Understanding BAME history
The report said the autonomy schools will have in deciding content under the new curriculum for Wales meant there was a risk that BAME themes would be marginalised.
"There is no statutory requirement to teach specific topics of central understanding to the histories of racism and diversity, for example, the histories of slavery or the Holocaust. This is of concern," the report said.
It added the new curriculum's focus on cynefin, the local area, "may not be helpful" in areas with few pupils from BAME backgrounds, where the "history is not regarded as part of the local environment".
Though there are significant regional variations in the percentage of Welsh pupils identifying as being from minority ethnic backgrounds, ranging from 34.4% in Cardiff schools to 4.1% in Anglesey, the report said there was ethnic diversity to be seen in all parts of Wales.
Education Minister Kirsty Williams welcomed the "challenges identified and potential solutions" in the report.
She said a national network of teachers and other key figures in education would help to identify gaps in resources, in order to make sure schools get the right support to implement the new curriculum.