on food groups, calories, saturated fat, and sodium, and that incorporate Dietary Guidelines for Americans and the Dietary Reference Intakes. Nutrition plays a critical role in cognitive development and academic performance for children; undernourished children are more likely to be less energetic and less able to concentrate. The day-to-day observation of teachers and administrators of the relationship between inadequate nutrition and behavior and the ability to learn is substantiated by scientific studies. Twenty Cape Town, South Africa, children were studied for 11 years, beginning in 1955. The study was based on the hypothesis "that the ill effects of under-nutrition are determined by (1) its occurrence during the period of maximum growth and (2) the duration of under-nutrition relative to the total period of growth. . . Evidence is cumulative and impressive that severe under-nutrition during the first 2 years of life, when brain growth is most active, results in a permanent reduction of brain size and restricted intellectual development." Some basic micronutrients are necessary for children to maintain a good status of learning, such as iron and vitamin B12. Iron deficiency puts a child at risk of cognitive delay and lower math scores. Food safety In December 2009, a report was released that showed that fast food restaurants were far more rigorous in checking for bacteria and dangerous pathogens in beef and chicken than the school lunch program. A 2018 study by USDA and University of Connecticut researchers compared data from mandatory safety inspections for ground beef for the NSLP and separate data from random USDA inspections. The study found that the beef destined for the NSLP had fewer levels of test failures than beef for the market generally, although a study author noted that "ground beef that fails the National School Lunch Program’s inspection can be sold to other vendors and eventually make its way onto consumers' plates." Between 2005 and 2014, there were no outbreaks of Salmonella and E. coli linked to beef provided to the NSLP, although there were dozens of such outbreaks in commercially sold ground beef over the same period. Participation rates In 1967–68, the national enrollment in public and private schools was approximately 50.7 million, according to a survey of School Food Services in March 1968. About 36.8 million children, or 73 percent, were enrolled in schools participating in the National School Lunch Program with an actual average participation in the program of 18.9