What is the name of a movie?

i don't recall the name but any one in high school will know because i remember seeing it like every year. it's about a dude that is able to go to Harvard university or some crazy university that is hard to go in to by probing that what they teach out of the books is fake. later on he becomes a teacher but at the same time he starts seeing things that are really not there. one of them is his best friend that is only imaginary but don't find that out till almost at the end of the movie, another hallucination is when he thinks he is a code breaker for the government. that's pretty much what i remember if any one knows the title to the movie i will greatly appreciate it. thanks.