I agree it is a people problem but: the people are ignoring you and the tech is just asking for abuse and that tech too was implemented by a bunch of people who are ignoring you. So absent an outright block on all such messages with the significant risk that one day you'll miss something important there isn't all that much that you can do. Complaining certainly doesn't seem to work (at least: it hasn't worked for me) and the only thing that happened in terms of change is that there now are two portals (and two apps...) to be used because half the teachers refuses to switch to the new one. It is frankly incredible how little attention is given to usability and respect for the user when the user is part of a captive audience. Short of changing schools there is not much that you can do and that isn't an option for a variety of reasons.