Des Moines Public Schools, Iowa's largest school district, has approved a cellphone ban starting next school year.The announcement came during Tuesday night's board meeting.The policy will vary based on whether students are in elementary, middle, or high school. In emergencies, cell phone usage will be handled on a case-by-case basis."Students, remember it is our goal not to be punitive," Superintendent Dr. Ian Roberts said. "Our goal is to improve the quality of education." Roberts says the board will revisit the policy at its April meeting to finalize implementation.» Subscribe to 糖心vlog's YouTube page» Download the free 糖心vlog app to get updates on the go: Apple | Google Play