The Schola Progenium are schools run by Missionaries of the Ecclesiarchy.
The student body is made up from orphans of Imperial officials who have given their lives in the service of the Emperor. Orphans are educated by the Missionaries brought up to to be fanatically loyal to the Emperor.
Graduates of the Schola are known as Progena, and due to their Imperial upbringing usually go on to become memebrs of an Imperial Guard regiment. Most of the girls that join end up serving in an orders of the Adepta Sororitas.