There is the shock when I first see it. But it depends on the teacher, the class, the educational environment, and many other factors, such as fashion, race, religion, gangster affiliation, politics, and family. Real Romeo and Juliet stuff.
Sometimes I think the teacher is a jerk. As a teacher I put every red (not green) mark as a signal. I correct mistakes; that is my job as a teacher. I try to make those red marks benefit the student with thirty years of my expertise. I do it to help.
Here in Los Angeles we have this: "Stand and Deliver". A movie about what the red (or green or black) marks really mean.