The effect on the ability of children to attend to their school work, of the size of breakfast and whether a mid-morning snack had been consumed, was considered. Nine year old children were studied for four days. They reported what they had eaten for breakfast and days when they either had or had not eaten a mid-morning snack were contrasted. For an hour in the late morning, while performing individual work, activity sampling was used to establish the time spent on task. Those who had eaten a small breakfast, on average 61 kcal, spent significantly less time attending to their work than those who had eaten larger meals. The adverse effect of a small breakfast was reversed by the consumption of a mid-morning snack.