SAM HANANEL | November 1, 2013 11:43 AM EST |

WASHINGTON (AP) — A growing number of part-time college professors are turning to labor unions to address complaints about low pay and lack of job security.

There is a move to unionize at campuses from Georgetown University in Washington, D.C., to Tufts University near Boston. It comes as colleges rely more heavily on adjunct faculty to teach classes.

Last month, adjuncts at Tufts became the latest to join the Service Employees International Union, which has been aggressively targeting college instructors.

The union plans more elections at colleges in the Los Angeles, Seattle and Boston areas.

Adjunct professors make up more than half of all college faculty.

Unlike full professors, they earn just a few thousand dollars per class, and their job status can change from year to year.