This research aims to determine the contribution of private schools to socioeconomic school segregation in Peru and its departments. A microdata mining is carried out of the National Student Assessment for the 2nd year of Secondary School, in such a way that it works with 631 013 Secondary School students, distributed in 17 310 educational services in the 25 departments. A greater segregation was found in the group of students with fewer resources, in terms of private school; while for those with greater resources, segregation is greater in public schools, although this segregation is considerably less. In both groups there are important differences between departments.