Priscilla Chan -- Genius Even Before Marrying Mark Zuckerberg

Priscilla Chan is no dummy ... in fact, Mrs. Zuckerberg was voted "Class Genius" back in high school ... way before she decided to hook up with a guy who would change the world.

Chan -- now 27 years old -- received the title during her days at Quincy High School in Massachusetts back in 2003. Priscilla went on to Harvard, where she met Mark and the rest is, as they say ... on her Facebook timeline.

The lesson here: Stay in school, study hard and you too may land a billionaire.