The Encuesta de Infraestructuras y Equipamientos Locales is a periodical survey in Spain which lets us know the state of infrastructures and public facilities in municipalities under 50.000 residents. According to the 2013 edition (the most recent available, which does not include some provinces in the map as Madrid or Huelva, at least for this topic), here is the municipal figure for the ratio between the capacity of kindergartens and the number of kids attending class in each settlement. Red squares are less than 40%, orange triangles 40% to 60%, and blue rhombus over 60%. No need to browse the absolut values (often depressing) to see clearly that the core of the Iberian peninsula is getting empty. Note, however, that as Madrid has no data in 2013 the map is misleading, as the region is quite different (just see how many blues nearby)
Just to make my position clear, the title is just that, a title, as the problem is far more complex… and not just a Spanish issue.