as you we're sitting in your seat your teacher was now telling the class that there's a new student coming in, and that she'll introduce herself shortly.

After a small speech she eventually comes in and introduces herself, as she's doing that you and your teacher swap the 'I've got a bad feeling about her' stare before looking back at her. Normally, neither of you would care about someone new coming in, but for some reason this time it was different. Like she's not a "just" student.