The establishment of charitable institutions devoted to taking in and indoctrinating the young and needy, arose from the wars and plagues that devastated Castille from the mid-fourteenth century. This reached its highest point during the reign of Henry IV, halfway through the fifteenth century. We are sure of the existence of the San Ildefonso School in this period and so this makes it the oldest educational institution for children in Spain.
Unfortunately, there are no documents to establish the founding date of the San Ildefonso School with accuracy. Jeronimo de la Quintana in his book "Historia de la Antigüedad, Nobleza y Grandeza de la Villa de Madrid" (1629) tells us of the school's oldest-known origins:
"In San Ildefonso school …… the so-called "indoctrinated children" are brought up ….Because of its great age it has been impossible to find out when it was first founded or by whom. The only trace of this school was in an endowment from the Catholic Monarchs in about 1478 when they graciously bestowed money upon it. This document is kept in the city's archives…"
The oldest preserved document is a documental reference to the "Provisión del Consejo" (ASA; 2-420-118) signed by Charles I in 1543, authorizing the town of Madrid to grant fifty "bushels" of wheat to the "indoctrinated children". Later documents give further proof of the great age of the institution: the appointment of Alonso Pérez as chaplain in charge of the "indoctrinated children" in 1547 and a Royal Warrant signed by Philip II in 1552.