Ranges from fluorescent yellow to pink. In addition to purchase, some teachers have approached local tennis clubs for donations of used tennis balls. Of course there are always the tennis balls from the roof of the school. Finally, some communities now include tennis balls as an item for recycling. Paradoxically, the elimination of noise has made the children more aware of noise, and communication has been easier in the classroom.
Children say it is easier to hear other children, and easier to pay attention in the classroom.