Teachers fear the findings may promote junk food and the results confound suggestions that high-sugar diets cause hyperactivity.
The scientists, however, believe learning would improve through small regular snacks rather than large lunches.
"The evidence sugar might cause hyperactivity is non-existent. We have shown it can help memory and concentration," Telegraph quoted Professor David Benton, as saying.
"Children between the ages of five and ten need twice as much glucose for their brains compared to an adult, but unlike other organs the brain does not store energy so it has to obtain it straight from the blood.
"The message we would like to encourage is that children need to be fed a little and often, but the risk is that they get fed a lot and often leading to problems with obesity," he added.
In the research, Benton gave 16 nine and ten-year-olds fruit squash containing either artificial sweetener or glucose, a basic form of sugar. When the children consumed glucose, he found their memory test scores improved by over ten per cent.
The children also spent between 11 and 20 minutes longer on a task when asked to work individually in class.
However, Benton insists that schools should not start feeding pupils fizzy drinks between classes, proposing regular fruit of muesli bars instead.