Content:
Informant – “The lore is that you can only go through the gate once as a Freshman and you can only leave through the gate as a senior or you won’t graduate.”

JK – “So how do you get onto the campus then?”

Informant – “This is just the main gate. There are other gates.”

Context:
Informant – “I heard it on an official college tour.”

Analysis:
When you are college student, your campus can feel like your whole world. You can lose track of the outside world and become totally immersed in your college’s culture. This superstition is an exaggeration of that feeling. You enter this new world as a freshman, and then you are trapped there until you graduate. Passing through the gate before graduation is like leaving the world too early (i.e. not graduating).