Bella Thorne and Patrick Schwarzenegger Surprise High Schoolers in Chicago

Students at a Chicago high school got quite a surprise on Monday when Bella Thorne and Patrick Schwarzenegger showed up unexpectedly.

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The duo is out and about promoting their new movie, "Midnight Sun," about a teenage girl who can't go out in the sunlight.

Knowing their target audience, Thorne and Schwarzenegger went straight to the source to whip up buzz for their new flick ... teens.

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Students from Nicholas Senn High School in Chicago, Illinois went wild for the stars. They snapped pics and took selfie videos with the actors and even got some signed swag.