49children (30girls,mean age in years: M¼5.26, SD¼0.29) from one public kindergarten of the City of BuenosAires in 2009
Children had a full time school schedule (8:45a.m./04:00p.m.), including nap time and three meals (breakfast, lunch, and an afternoon snack). Attrition rate from pre-topost-cognitive assessment evaluation was 0%.
The school also had primary-school education, which allowed us to collect data on the children's academic achievements during the year that followed the intervention. We lost contact with22 participants during the follow-upstage of the study (attritionrate 44.89%) because these children moved to other primary schools. Children in the control and intervention groups continued in the same classes during their first year of primary school (that is, children in the control group were not mixed with children from the intervention group during first grade). Therefore,to diminish the potential effect soft he influence of the primary school teachers on academic-grade assignments (“teacher effect”) we included two external control groups, one per classroom(Table1).