A 3-foot-long ball python escaped from its cage inside a Wisconsin high school – and is believed to be hiding out inside a science lab ventilation system, school officials told The Post.

Kai, a three-foot-long ball python was on the loose somewhere inside the school premises after it escaped its cage by knocking off its lid.

As freshmen showed up for their first day of class at Fond du Lac High School Tuesday morning, one of the school's inhabitants was AWOL. A ball python named Kai had slipped from his cage sometime ...