The General Education Law was approved half a century ago. It was designed by Francoism to reform the educational system, adjusting itself to the liberal-developmental approach that Franco's regime followed in its last few decades. The oppression that the so-called "vernacular languages" were subject to during the former years of Francoism made their learning recognition stand out amidst the rest of the changes and developments that this law provided. The aim of this paper is to review the concepts and measures that structured Francoist educational politics in regard to languages. Special attention will be paid to the causes, foreseen in the "Libro Blanco" (Spanish for "White Book"), that fostered the change established in the 1970 Law. The idea will be presented that the incorporation of regional languages in the new policies happened to fulfil the idiomatic regulations requested by UNESCO and the Catholic Church, and to meet the need to cope with the popular currents of linguistic demand emerging in the scenario of socio-labour conflict that characterised the final years of the dictatorship. This moment was determined by the tensions generated within a system reluctant to change its traditional values, although it was forced to resolve the external and internal pressures that urged it to recognise the multilingual reality of the Spanish State in schools.