Although trends in the racial segregation of schools are well documented, less is known about trends in "income" segregation. We use multiple data sources to document trends in income segregation between schools and school districts. Between-district income segregation of families with children enrolled in public school increased by over 15% from 1990 to 2010. Within large districts, between-school segregation of students who are eligible and ineligible for free lunch increased by over 40% from 1991 to 2012. Consistent with research on neighborhood segregation, we find that rising income inequality contributed to the rise in income segregation between schools and districts during this period. The rise in income segregation between both schools and districts may have serious implications for inequality in students' access to resources that bear on academic achievement.