I am not sure where your child goes to school but my child does not have snacks in his Kindergarten class. They have Breakfast and Lunch. They usually only have a snack if there is a party. Although he is only in school until 12pm. I would not say it is a disiplinary action but would say it is something that they are doing because a child is there to learn and not it is not play time anymore. I am fine with my son not having snacks at school because I feel it would take away from his education time.
Yes, I believe it is. However, when my son's school used it to control his behavior and sent him to the Principal's office he "visited" classrooms on the way. The school responded by giving him a snack if he went to the office without disrupting other classes. It seems to me they were rewarding him for bad behavior. He was in Kindergarten when this ocured.