The evolution of compulsory schooling in Spain: a guide for the implementation of causal designs

From the Public Instruction Law of 1857 to the Organic Law on the General Organization of the Educational System of 1990, various legal provisions have regulated the period of compulsory schooling in Spain, as well as the structure of basic education and its connection to subsequent stages. This paper conducts a historical review of said legislation, documenting with historical statistics the impact on enrollment rates of the different provisions that regulated the minimum school-leaving age during the second half of the 20th century. In particular, detailed information is provided regarding the cohorts subject to different legislative frameworks, together with a description of the geographic variation in the implementation of these legislative developments. In doing so, this work aims to serve as a guide to inform future research seeking to estimate the causal effect of such reforms, or research attempting to use educational legislation as a source of exogenous variation in years of schooling to estimate the causal effect of education on other variables.