Universities, local school districts, and other educators are fighting to hang on to a slice of airwaves the Federal Communications Commission may want to repurpose for commercial 5G networks.

The FCC is scrambling to free up spectrum for AT&T Inc., T-Mobile US Inc., and other carriers to help them deploy the networks ahead of China to maintain the U.S. lead in wireless innovation.

Long before broadband, the commission set aside spectrum in the 2.5 GHz band for colleges and other...