Why are Gossip Girl and her friends checking their mailboxes in the novel, I Like It Like That?

In this story, Gossip Girl talks about the latest subject that is on everyone's mind. The high school seniors in the crowd are all worried about where they will be going to college and more importantly, if the colleges of their choice will accept them. Everyone is making the dreaded visits to the mail box to see if "that" letter has arrived yet.