Because of the bad air, classes will not be held at most, if not all, schools in Nevada County on Friday. We’ve confirmed that the list, so far, includes the Nevada Joint Union High School District, the Grass Valley School District, Union Hill school, as well as the County Office of Education. High School District Superintendent Brett McFadden says decisions will be made on a day-to-day basis. But the Sierra College Nevada County campus in Grass Valley already cancelled classes on Thursday, and there will also be no classes on Friday. But officials say they expect to resume normal operations on Monday.