IOWA CITY — Student activists in Iowa City plan to walk out of class on Friday, six years after the massacre at Sandy Hook Elementary.The walkout will begin at City High School, and students will walk to the Ped Mall “as a proactive step against our state’s lack of gun safety legislation,” organizers said on the walkout’s Facebook event page.The event is expected to begin at 2:26 p.m., the same time that the shooting happened on Dec.