Imperfect whether it's true or not about sugar rush, I see the same thing frequently, although a clamp down on lunch box contents has improved this. To be fair, I can see the difference in some children in the mornings on the days they come to breakfast club -cereal, toast, milk and fruit, so perhaps some quiet morning children just haven't eaten.
Interesting reading M0nica and Deedaa's comments.
Scientific fact or not, when you're dealing with children who are 'high' it's just as easy to think high carb and sugar intake as it is to think badly behaved children and much more preferable.
Army horses loose on London streets
