a friend of mine is a math teacher, the same to me, he has been annoyed with noises of cell phones in his classes for a long time, you know the naughty students , make phone calls or send messages and so on, i am troubled with the dins of cell phones when i am at home. so he and i bought a cell phone signal jammer from www.jammerall.com. share it with you, hope can help you  with your children.