Some schools that don't have universal chromebooks allow students to use cellphones for classwork, such as math classes. Not everybody has a personal laptop or chromebook, and not all school districts have chromebooks for every student. Not doubt cellphone usage is a problem, but to tell teachers that kids simply can't use them at all is likely to cause problems. And where in the article does it mention just personal laptops? The wording seems pretty vague to me, and is likely to cause confusion unless it is clarified.