A senior prank has left six high school students suspended, fellow students outraged, and a custodian unemployed.

Students in Clayton, Ind. said the prank involved putting 12,000 Post-it notes on windows and walls of the school, and was intended to be harmless.

“We figured it’s cheap, easy, creative, it doesn’t damage anything,” said Anthony Canaday, one of the suspended seniors.

Other students are protesting the suspensions and firing of the school janitor by staging a sit-in in the school gym.