In this paper we document gaps in math and reading achievement between children whose mothers have completed at least upper secondary education and those who have not, using test scores from third and sixth graders across multiple countries in LAC, in 2006 and 2013. There are substantial differences across countries in these gaps, and there are also differences in how they change over time. Interestingly, differences in these gaps are not correlated with differences in income inequality across countries. They are however strongly correlated with the levels of socio-economic segregation across schools in different countries.