 Speed limits in school zones are 15 miles per hour. Seatbelts are a must, click it or ticket. Classes start on Thursday, August 1st in the Prescott and Humboldt Unified School Districts, while students in the Chino Valley Unified School District return on Monday, August 5th. I'm Bill Monroe reporting. As it prepares for the start of classes, the Humboldt Unified School District is hosting back-to-school events next week.