The process of linking the district or student BYOD devices to ClassHub is called enrollment. Once a device is enrolled in ClassHub, it does not need to be re-enrolled unless it is restored, reimaged, manually unenrolled or deleted in the ClassHub Settings portal under Devices.
Note: ClassHub functions as an MDM server to provide the macOS features of ClassHub. Apple only allows a macOS device to be part of one MDM. If you’re utilizing another MDM server with a macOS device, the device must be unenrolled from the former MDM to be part of ClassHub.
You can view the full instructions for enrolling macOS devices here: http://docs.classhub.com/ClassHub-Student-Enrollment-MacOS.pdf