Yeah seconding this both as a parent and someone who has worked in education IT (K12 and higher ed) for almost 15 years. I'm not familiar with GoGuardian but I do recall with certain 3rd party Google apps that did similarly there were ways within the admin console for said app to exclude monitoring devices (regardless if managed account that's logged in) unless they were on the district network(s) by adding CIDR blocks to a whitelist. Of course, if someone were to use the device on a BYOD network in district you could then get scooped up in that dragnet though we excluded even those networks to prevent this as all district devices should be connected to the proper LAN.

I've personally forbade my kids from logging into devices we own with their school accounts (O365). I've also gone so far as to relegate them to only connecting to a segmented guest network (internet only) with their district issued devices. I no longer work for a district but provide various levels of support for districts in my county as a state employee and let me tell you, no one really knows what they're doing. A district I used to work for uses a product called Aristotle essentially logging key strokes of every staff member and student. There are, or were, certain school admins that made it their business disciplining bored-ass students for things 99% of the time they may have said in jest to a fellow student. On the flip side it was instrumental in catching a couple staff members that were doing some pretty heinous things, one of which who is currently serving 35 years on federal charges.