"La ĝemeloj studas en apartaj mezlernejoj."
Translation:The twins are studying in separate high schools.
I think it's to do with the traditional view of schooling: primary, secondary, tertiary.
I'm not sure what the status of middle schools is around the world. In Australia, 20 years ago they barely existed; it was primary (R-7) then high school (8-12). They're becoming more common now.
Manĝu terpomojn kaj feliĉiĝu!