Not always. There's a time and a place for including end users in your threat model. These would include scholastic and carceral settings, where in both cases the end user may, as an example, desire access to resources that have been deemed inappropriate.
I disagree that a software in a school setting should see students as adversaries. Cheating is a much higher level problem that is better dealt with education and negative reinforcement. After all, those students will need to become participants in a society where we definitely don't want this level of mutual distrust around every corner.
But in any case, students are usually NOT the customer here even if they are the end user.
