Phillip Malloy is pretty much a nightmare student for any teacher. Constitutionally lazy and forever goofing-off in class, he's virtually unteachable. It's not so much that he's lacking in intelligence, as it is that he's not prepared to use it in his academic studies. Philip's almost the epitome of a high school jock, and his main focus in life is the track team.
But it's not enough that Philip neglects his own studies; he has to disrupt other students' learning too. His constant humming of "The Star-Spangled Banner" leads to a showdown with Mrs. Narwin, which ultimately generates something of a media storm. Philip falsely accuses Mrs. Narwin of preventing him from singing the national anthem, and the ensuing negative publicity forces her to take a reluctant sabbatical.
What this whole sorry episode illustrates is the way that Philip's always prepared to put his own selfish needs before every one else's, both fellow students and teachers alike. He doesn't take his studies seriously, so why should anyone else be allowed to? This flippant attitude to life and learning is what makes him such a bad student more than anything else.