Anyone who has felt a little wobbly in the late afternoon understands the value of grabbing a quick snack as an energy boost. Apparently, some public schools in Virginia are applying a similar principle in preparing students to take the statewide achievement exams.

A recent study found that schools in 23 districts around the commonwealth increased the calorie count in school lunches on Standards of Learning test days. By sweetening desserts or offering some deep-fried delights, schools with a history of test-score problems augmented calories by an average of 18 percent.

"At first blush, one might question the plausibility of schools using the nutrition margin as a way to improve student test scores," write study authors David N. Figlio and Joshua Winicki. But they note that there is a "well-established link between nutrition and short-term cognitive functioning" and that subsidized lunches are most likely to go to lower-income kids who score poorly on exams.

They found that the schools had raised math, social studies and English test results by as much as 11 percent. School administrators and food service directors said they were aware of the link between a quick carb fix and sharpened concentration, but Charles Pyle, of the Virginia Department of Education, says, "There certainly isn't any policy on the part of the state to encourage schools to serve certain items out of any belief that this is going to have any measurable impact on student achievement on the tests."