Santín González, DanielSicilia, Gabriela2023-06-172023-06-1720180003-684610.1080/00036846.2018.1470314https://hdl.handle.net/20.500.14352/19044The non-compulsory and non-free of charge character of preschool education level before 3 years old in Spain raises some doubts about the exogenous nature of this variable. This article provides new evidence about the impact of preschool years on educational outcomes by exploiting a peculiar Spanish database that supplies information on two classrooms at fourth grade in primary schools where students were randomly allocated into each group. Using an identification strategy that reproduces a natural experiment, we find that belonging to the group with more average years of preschool education significantly and positively impacts on fourthgrade students’ average outcomes. Particularly, an increase of one standard deviation in the difference in years of preschool attendance results in an increase of 0.16 (0.13) standard deviations in the group achievement for mathematics (reading). In view of the importance of preschool education and considering that preschool attendance before 3 years old is related with socio-economic variables, we conclude that extending free preschool education to the 2-year-old age group in Spain should be considered especially for students in families with less favourable backgrounds.engjournal articlehttps://doi.org/10.1080/00036846.2018.1470314restricted accessC50I21H52Preschool educationStudents’ outcomesNatural experimentPublic expenditureEconometría (Economía)Economía públicaEducación5302 Econometría58 Pedagogía