" The introduction of a diet policy which lowered sucrose, synthetic food color/flavors, and two preservatives (BHA and BHT) over 4 years in 803 public schools was followed by a 15.7% increase in mean academic percentile ranking above the rest of the nation's schools who used the same standardized tests. Prior to the 15.7% gain, the standard deviation of the annual change in nation percentile rating had been less than 1%. Each school's academic performance ranking was negatively correlated with the percent of children who ate school food prior to the diet policy changes. however, after the policy transitions, the percent of students who ate school lunches and breakfasts within each school became positively correlated with that school's rate of gain (r = .28, p < .0001)."
The first major diet policy revisions restricted sucrose levels to 11% in all foods during the fall of 1979. Two synthetic food colors were also eliminated. In the spring of 1980, mean national percentile rank rose to 47.3% - an 8.1% increase (s.d.=.20). During the 1981 academic year, the remaining foods containing synthetic colors and all foods with synthetic flavors were eliminated. Rank increased 3.8% to 51.2% (s.d.=.10)
During 1982, no further revisions were made. Mean national percentile rank declined slightly to 50.8% (s.d.=.01). However, when foods containing BHT and BHA were eliminated during the fourth year, rank increased to 54.9 -- a 3.7% increase (s.d.=.20)."