@GMTplus7 Racial and ethnic divisions generally have a similar effect. The reason that race matters in HS is because some groups (AA/Hispanic/especially Native Americans) tend to attend schools with fewer resources, come from families where their parents don’t provide much support, have trouble learning due to linguistic issues in some cases or cultural exclusion in others, and thus perform worse on average than a typical WASP kid. In the Baltic nations, ethnic Russians tend to attend schools with fewer resources, come from families where they don’t get much parental support, find themselves excluded as a result of linguistic and cultural barriers, and thus perform worse than ethnic Estonians/Latvians/Lithuanians.
Maybe Russians and Latvians are both largely white, but an ethnic Russian in the Baltics generally won’t be in a better situation to succeed in school than an underprivileged son/daughter of recent immigrants is in an English-speaking school. Ethnic Kurds in Syria may be Arabs, just as the country’s Alawites are Arabs, but that doesn’t mean the former don’t face disadvantages comparable to those of URM students in underperforming schools.
The only way one can argue that an underprivileged ethnic group is at less of a disadvantage in school than an underprivileged racial group is by asserting that there’s a difference of ability between different races, and I doubt that’s the point you’re trying to make.