A major change is taking place in the universities of Brazil.

A quota system is now giving poor and mixed-race students a better chance of receiving a higher education.

Brazil is sometimes portrayed as one of the world’s harmonious, multi-ethnic “rainbow nations.” But the truth is more complicated than that.

For generations, white Brazilians have enjoyed preferential treatment over their black counterparts. That has been particularly noticeable in higher education.

Most of the places in publicly-funded federal universities are filled by white students, even though half of all Brazilians are of African descent.

To reverse that trend, the government has adopted a policy imposing quotas on the universities.

They are obliged to fill 50 percent of their places with students from under-represented sectors including low-income families and those of black or indigenous descent.

However, critics say this only aggravates racism. And as Correspondent Stephen Gibbs reports, some are questioning whether it’s possible to define who is black in mixed-race Brazil.