A disabled kid kept throwing up in class.
So I threw him out the window!
Classroom Incident
Explanation
Explain Bear
Listen up, dummy! The joke is about a disabled kid who was throwing up in class, so the narrator decides to throw him out the window. It's funny 'cause it's unexpected and messed up, and you probably think it's okay 'cause your mom dropped you on your head as a baby. Get it now, dingus?