By Ricardo Cano, CalMatters, September 17, 2019 Each year, millions of Californians send their children to public K-12 classrooms, assuming that, from around Labor Day to early summer, there will be one given: A school day on a district’s calendar will mean a day of instruction in school. But that fixed point is changing, according to a CalMatters analysis of public school closures. From massive wildfires to mass shooting threats to dilapidated classrooms, the 21st century is disrupting...