When classes change nine times a day, Yorktown secondary students cross Highway 72, dodging 18-wheelers and heavy traffic, to get to their Ag and career classes at the building by the bus barn.“This is a recipe for disaster,” Gerald Nixon, YISD superintendent, said. “It’s even more dangerous when the weather is bad.”Withthe$20,000,000 bond election on the May 4 ballot, YISD’s purpose is “safety…