I agree with your point, however, I think the majority of teachers and even lecturers are simply uneducated, when it comes to avoiding surveillance of their students. When presented these issues, most shrugg it off, because they fear having to actually do something about it themselves. They carelessly throw away privacy of their students by suggesting to use the usual suspects for voice and video chat. In my opinion in this age of technology, getting educated about the issues here should be a mandatory aspect of the training of all people, who want to be teachers.
Then there is this illusion, of setting up something oneself, as an institution, being super difficult.
Schools could easily rent a decent server, costing something like 40-80 dollar/euro per month and protect their students. They do have an computer/IT/informatics teacher, who studied computer stuff, hopefully. If not, they could hire someone to do it, the country / state could finance it, or they could even get a talented student to set it up for them. The setup itself is really not that difficult and takes an afternoon or without much prior knowledge perhaps 2 days. And really, if it is a money question, just ask parents to donate and the school will be covered. No unsolvable problem at all.
Universities easily have the cash to rent servers and usually have IT people in employment as well, who manage all sorts of stuff. It should be an easy task for them to set up a privacy preserving text, voice and video chat.
Then you have the problem, that I experienced myself, when I wanted to make it happen for schools, contacting someone I know at a school: There is bureaucracy in the way, which demands a uniform solution for schools. Which results in using a centralized service provider, because the whole country (!) does not manage to set up the infrastructure for its students. Just imagine that. A whole country, incapable of setting up privacy preserving solutions for students, all the while everyone is whining about bad online teaching during the pandemic. Somehow this makes me doubt their motivation and willingness to solve the problem.
Unfortunately most people are not informed about the issues and choose to continue being uninformed that way. They do not want to deal with ethical questions and rather want to throw money at the problem, by purchasing licenses for surveillance products.
All it takes is people caring.