Education Lab is a Seattle Times project that spotlights promising approaches to persistent challenges in public education. The Seattle Foundation serves as the fiscal sponsor for Education Lab, which is supported by grants from the Gates Foundation and Ballmer Group. Learn more about Ed Lab and subscribe to our weekly newsletter . A new districtwide cellphone policy will go into effect for Seattle Public Schools next week, Superintendent Ben Shuldiner confirmed Wednesday evening. Starting Monday, no phones will be allowed during the entire school day for all elementary and middle school students. For high schoolers, the policy is less strict — they won’t have phones in class but will be allowed to have phones during passing periods and at lunch. Exceptions to the policy will be honored for students who require access to devices for medical needs. The policy doesn’t apply to smartwatches. Current cellphone policies are a patchwork, with each school setting its own rules.…