Sentence:  Dr. Clark has served as teacher and principal in Oklahoma high schools , as teacher and athletic director at Raymondville , Texas , High School , as an instructor at the University of Oklahoma , and as an associate professor of <WSD>education</WSD> at Fort Hays , Kan. , State College . 
Meaning of the word marked with <WSD> tags:  the profession of teaching (especially at a school or college or university)