The Sue Sylvester Shuffle - S2-E11
Continuity mistake: When the Warblers are singing "Bills, Bills, Bills", one of them throws the sheets of music up in the air as he spins. For the remainder of the song, the sheets are on the floor during some shots, but have disappeared in others.
Answer: The show is purposefully stylized and over the top. It is not designed to be an accurate, realistic representation of American high school. The idea that the glee club is so unpopular other students can literally throw garbage at them with impunity is an over-exaggeration of how glee club is considered "un-cool" compared to things like football. However, there is a second way of looking at it. The audience is simply never shown anyone getting into any trouble for throwing slushies. Just because we don't see it doesn't mean it never happened.
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