All sorts of things can ruin a principal’s day. A misbehaving student. A fire in the cafeteria kitchen. A teacher having a meltdown.

And then there’s Nicki Minaj. On Thursday afternoon, the rapper known for her racy lyrics, avant-garde fashion choices, and un-self-conscious celebration of her physical assets posted on Twitter, where she has 18.1 million followers, that the principal of her alma mater, Fiorello H. LaGuardia High School of Music and Art and the Performing Arts, had turned down her offer to speak there.

“I wanted to go back to my HS and speak to the students but the new principal declined,” Ms. Minaj, 31, wrote. “No need for me to inspire them, I guess.”

“That school changed my life and I wanted to pay it forward to the students there now,” she added. Both LaGuardia students and Ms. Minaj’s fans reacted with anger and disbelief on Twitter.