
He is a college kid tho.
There is no such thing as a part-time highschooler and most schools strictly forbid parttime work plus they have school uniforms. These guys are wearing casual clothes and go work without it being a deal, plus they have credits (which is a college thing, not a highschool thing).

I'm pretty sure that's a dumb translation error. Because, as I said, nothing regarding the students or school says anything BUT college (they have nurses there too, mind you). And I checked, highschool/school (koukou) and college or university (karejji or daikaku) have different words in japanese as well.
My best guess would be that the character just said 'school' and the translators didn't bother with context (which is sadly often the case) and just assumed it means highschool instead of a student just naming whatever school-type place they go to as simply 'school'.

This is at a high school. There's mention of them not wearing uniforms like the other students, Japanese universities don't have uniforms. The classrooms totally do not look like lecture halls either lol. I'm guessing they're just students that weren't able to complete school in time or couldn't rack up enough credits.

I checked real quick. There IS joined schools that combine college education and highschool, so it could be one of those.
And again, highschoolers always wear uniforms, college students don't. In these joined schools it's likely the same.
I'm pretty sure given the decent writing, the author WOULD have adressed the school being something as out of the ordinary as a joined school or such. Since even for the japanese this is likely not a common or familiar setting. They usually adress these if they use something out of the norm.
One way or another, this is definitely not an underage kid and his behavior doesn't match that of a highschooler but matches well with what we usually see for a college student.
Shame that there wasn't some sorta info page or info card as soon as the characters show up. That would have been useful. XD

Yes, honestly I was so confused at first because I'd never heard of the concept of part-time students before. I think what's important though is that Amamiya is an adult (legal age in Japan is 18, since there's a 7 year age diff he's ~19). Though I am somewhat concerned about the maturity gap I chose not to think about it too much since it's just a short simple yaoi, these stories usually disregard these nuanced matters.

Same here, that was REALLY weird and I had to re-read just to make sure my eyes didn't trick me. X'D
I think maturity-wise they should be perfectly fine. The love interest does have his childish side to him, being all cutesy and puppy-like in some moments, but generally he seems well put together and mature. That's why he's purely giving me college student vibes. Highschoolers with a 'mature aura' are usually quite different. Can't quite explain how/why. Can't put my finger on what exactly it is and how to explain it. ( ̄∇ ̄")
I thought he was a college student not a high schooler
Not that it stops me from reading a story and he is a fourth year so senior in hs maybe 17-19 idk how it works in Japan and i dont ever remember seeing fourth year being said in a high school manga before
but now im judging the nurse for falling for the whims of a high schooler