Shazam 1981 Star Master and the Solar Mirror

An evil alien known as the Star Master threatens earth. When the Marvels confront him, he captures Mary and Junior. He then send an ultimatum to the United Nations: surrender Earth, or else he'll destroy it. The U.N. refuses to bow to his demand and plan to launch a rocket that can project a force field, but they need to know where he's planning to strike. Captain Marvel then goes to Hero High to enlist the aid of some of their students.