Highland High was where Daria Morgendorffer attended ninth grade with Beavis and Butt-head, Cassandra, Stewart, and Earl. We know that Daria was an unpopular brain here; insulting notes have been stuck to Daria's chair (and once on her back) in some issues of the Beavis and Butt-head comics, implying she was bullied; and in "Boxing Daria", she says her parents were called in during ninth grade because she wrote "violent revenge fantasies". In the alternate reality of "It's a Miserable Life", she had a boyfriend (Martin) at Highland High.
Among Daria's teachers at Highland High was Mr. Van Driessen, Mrs. Dickie, Mr. Herrera, an unnamed Home Ec teacher, and Coach Buzzcut, and it was run by Principal McVicker. Van Driessen taught a surprisingly large number of subjects (even subjects that previously had other teachers), and so did Buzzcut from time to time.
The episode "Incognito" indicated there were problems with violence at the school: Van Driessen had confiscated guns off kids and people were only mildy phased by gunfire in class. Daria was there when classmate Earl was the target of a shooting.
Highland High was visited by President Bill Clinton as part of his "Youth: The Next Generation" drive. Daria was one of the smarter kids chosen to meet Clinton and ask him questions. ("Citizen Butt-head")
The school has a swimming pool and the cafeteria has a regular Taco Day. The football team's main rival is a school called "Tech". Several times it's done charitable work alongside Clark Cobb's Christian Businessmen's Association, which Daria had been drafted into. The school paper is called the Highland Herald; Daria worked as the fashion reporter ("because I'm a girl!") for a while.