One study from a developing country, Guatemala, found that poor growth during infancy, rather than low birth weight, was negatively related to adolescent performance on cognitive and achievement tests.[29] A later related very long term study looked at the effect of giving 6–24-month-old children in Guatemala a high protein-energy drink as a dietary supplement. A significantly positive and fairly substantial effects was found on increasing the probability of attending school and of passing the first grade, increasing the grade attained by age 13, increasing completed schooling attainment, and for adults aged 25–40 increasing IQ test scores.[30]