The NFHS contracts out the installation of the cameras. The school only has to provide an electrical outlet, internet connection and place to mount the computer. The installer does everything from running the cables, hooking up the scoreboard connection, mounting the camera, etc...
Each camera has to be calibrated for the sport (difference between even volleyball vs basketball in same gym), lighting, field type, motion detection sensitivity, etc...
Let's just say that some installers are better than others.