By one particular group of students. The majority of the school just ignores him. In the Raimi film, almost everyone is picking on him but Harry/MJ. The other nerds wouldn't sit with him.
As for the scientists, that was because they didn't see Peter get bit. They thought he was acting so weird for no reason.
I would say he was. Again, the bus driver and geeky girls picked on him. The guy was even invisible and getting picked on in college, something college Peter has outgrown by then. Heck, comic book Peter was friends with Flash in college/by the end of high school.
It's not necessarily unrealistic; my point is that it's extreme even for Lee/Ditko Peter Parker.
