Senioritis

Senioritis is a disease that affects approximately 95% of the senior population during their second (and last) semester of high school after receiving acceptance letters from the colleges/unversities of their choice. During this time, affected persons may experience lack of motivation, a major decline in fucks to give, and a burning passion to get the hell out of high school.

John: I haven't handed in that Biology assignment yet.
Mallory: That was due 3 weeks ago!
John: It's not me, it's the senioritis.