Before students and teachers can safely head back to Colorado’s classrooms amid a pandemic that is beginning its sixth month, school and health officials say they need a detailed map of where the virus is and how it’s behaving on any given day. Only frequent and reliable testing can provide that level of insight into a disease that has already dramatically upended the way schools operate in Colorado, with many delaying in-person instruction this fall as the state’s coronavirus caseload eclipses the 50,000 mark. But offering affordable and comprehensive testing and tracing is no easy feat for the state’s 178 school districts, which serve more than 900,000 students.