UNDATED (AP) – Data from the CDC on the new K-12 school year bolster the agency’s recommendation for masks in schools and in-person classes. One study in two Arizona counties found coronavirus outbreaks were almost four times more common at public schools without mask mandates on the first day than at those that re-opened with a masking requirement. Another study found case rates in children and teens increased more in U.S. counties where public schools had no mask mandates than in those where schools had that requirement. These studies lacked data on other measures that could have influenced the results. A third study counted 1,801 coronavirus-related school closures through mid-September, most of them in the South. Still, 96% of U.S. public schools have remained open with in-person classes.