Senioritis

Noun. A crippling disease that strikes high school seniors. Symptoms include: laziness, an over-excessive wearing of t-shirts, sweatpants, athletic shorts, and sweatshirts. Also features a lack of studying, repeated absences, and a generally dismissive attitude. The only known cure is a phenomenon known as Graduation.

Why didn't you study for Mr. Hames Test?

Oh, who studies for a test anyways. I got senioritis.