There is a strong association between the educational status of the parents and that of their offspring, which is what social scientists refer to as the degree of educational mobility. In contemporary Mexico there are 4.7 million illiterate individuals in Mexico and 1.29 million children (ages 7 to 15) liveing in households which had at least one illiterate parent. Of these children, 0.56 million were illiterate themselves.


Evidence points that access to early education acts as a leveller for family, social and economic background differences. That is, living in disadvantaged environments early in life is a strong predictor of economic and social outcomes in adulthood with evidence suggesting that 50 percent of the variability of lifetime earnings is determined by age 18 (Heckman 2016).
Since newly acquired skills build on top of previously acquired skills (educational skills build in a hierarchical or cumulative manner), children who fail to become literate start their lives with an early disadvantage of large consequences. This theory of skill formation also suggests that the return to investment in schooling decreases as academic progression takes place and that compensating for early education gaps can be very costly. Redistributing resources toward early years boosts productivity, fosters intergenerational mobility and reduces inequality.
Rather than to invest in compensating disadvantaged individuals later in life, the public sector should invest in the prevention of those disadvantages from emerging in the first place. Doing the opposite harms deprived individuals and is highly inefficient. The idea is that disadvantaged children who fall behind might never catch up or it will be costly to do so.
Bauer and Riphahn (2009) find also that the timing of school enrolment is related to the degree of intergenerational mobility: when enrolment occurs at an earlier stage in life, educational mobility tends to be higher. This is in line with the idea that early investments are harvested over a longer horizon than those made later in the life cycle. Human capital is synergistic.
References:
Bauer, P., Riphahn, R., (2006). Timing of School Tracking as a Determinant of Tntergenerational Transmission of Education. Economics Letters, 91, 90–97.
Heckman, J. (2016). The Economics and Econometrics of Human Development and Social Mobility. CEMMAP Masterclass.
Heckman, J. (2006) Skill Formation and the Economics of Investing in Disadvantaged Children. Science, 312, 1900-1902.
Heckman, J. and Carneiro, P. (2003). Human Capital Policy. Institute for the Study of Labor (IZA), Discussion paper no. 821.