Slovakia has been referred to the EU Court of Justice for failing to effectively tackle segregation of Roma children in education.
The European Commission referred the country to the court on Wednesday after it was found not enough had been done to deal with the problem.
Although the EU strictly prohibits ethnic-based discrimination, Roma children in Slovakia are often placed in special schools for pupils with mental disabilities and those who do attend mainstream education are segregated, often being put in separate classes.
Slovakia has the highest level of Roma segregation in education of any EU member state. According to the Roma Survey of the European Union Agency for Fundamental Rights, 65 percent of Roma pupils aged 6 to 15 attend schools where all or most pupils are of the minority - a 5 percentage-point increase on 2016.
The European Commission said that although Slovakia had tried to deal with issue through reforms and action plans, steps taken had been insufficient.
Slovak courts have previously confirmed segregation at schools.
In a ruling in December last year, the Slovak Supreme Court said Roma children who attended a primary school in Stará Ľubovňa, north-eastern Slovakia, were victims of discrimination.
In a similar case a primary school in Šarišské Michaľany, north-eastern Slovakia, was found to have discriminated against Roma children by separating them from other pupils.