We are often asked why we do not have a setting so that only Chromebooks managed by the domain are tracked or why we don’t have access to device level information such as serial numbers or MAC addresses. This is actually a limitation on extensions that does not allow them to have access to this kind of device level information.
Because of this limitation and the fact that GoGuardian cannot access device information to see if the device is managed by your domain, it is possible to have personal Chromebooks monitored and tracked by GoGuardian. Because the GoGuardian extensions are pushed to the users in your domain, these users will be monitored and tracked when signing in with their school given GAFE email accounts into any Chrome device (Chromebook or Chromebox) or when signing into the Chrome browser (only if you have the Chromebooks Only privacy setting disabled; it is enabled by default).
Your best option for not tracking personal devices is to search for this user in All Users and find the listing where they logged into a personal device (there will be two listings; a new listing is created every time a user logs into a new device) and to select the button in the top right under their name that says Stop Tracking User on this Device. This will prevent them from being tracked on their personal device, but will not affect them being tracked on the school device.