Let's say somebody wants to stop attending college momentarily because he is mentally unfit to continue, then who does he(or his parents) need to meet to unregister? I tried doing a search using words like "Head of department of student affairs" but it turns out that that is not the department I'm looking for.
I don't think a student would 'unregister' if they wish to stop attending the college momentarily as you say. They would obtain a Leave of Absence, which allows the student to temporarily leave while still remaining registered so they can continue later on. That's because being removed from the register is a pretty big deal that is more permanent. https://www.bestcolleges.com/blog/leave-of-absence-college/
Also, unsure of the US system, but in the UK and Australia, you would tend to have a member of the faculty be your tutor for smaller group work. This would probably be the first port of call over here? It would be bit more personal, as the faculty member would know you to some degree and be able to discuss what's going on a more personal level (hopefully!).
My college had the ungainly titled Omsbudsperson who acted as a go between for students who needed help resolving issues with the university.
These days any kind of education establishment seems to be a convoluted system of people with the vaguest job titles. With the day job, if I need to contact someone from a school regarding a student, the parents give tend to give me about six names of people it could possibly be. They're all head of this or coordinator of this or manager of the other.
I believe the point of contact would be either the Dean of Students or the Registrar. If one of those offices isn't the correct one, they would certainly be able to offer a referral.
When I dropped out of college for an injury, I contacted the enrollment offices. But then again, I also dropped out within a permitted time span. I would suggest choosing a number of colleges around the country where your story is taking place and checking what their withdraw procedure is. I've never seen a college that doesn't have that posted.
if its a momentary thing, students are allowed to not register for classes for another semester. I knew students who did this and i knew athletes who did this, too. They spoke with their course advisors. they weren't dropping out. they just werent registering for classes for the upcoming semester. the only thing about that is, if you arent taking classes, you cant live on campus. at least, on my campus, you had to be a full time student to live in the dorms. I think there is a time span between when you stop taking classes and start again. if you dont register for classes for a length of time, then they drop you all together. ETA: when i wanted to drop my major, i went to my course advisor, not the registrar
Does he need to unregister? In my experience in the US, most people leaving college do so by simply not signing up for the next semester. If he's on a specific degree track and intends to return, he'd want to talk to his advisor and make a plan for picking back up again. If it's mid semester and he doesn't want to fail the classes he's currently taking, he'd speak to his profs about taking an incomplete.
