Dennis was a Social Studies educator at Homewood-Flossmoor High School for thirty-five years. He began his teaching career in 1967 after earning his MS in Education/History and Social Studies from Illinois State University in Bloomington/Normal.
While at HFHS, Dennis taught history and was the head coach for both the boys and girls soccer teams for twelve years. In addition, he served his fellow teachers as president of the teacher's union for twenty-five years. He has served as a University Supervisor of student teachers at NIU since 1970.
Dennis is married and has two children, two grandsons and a granddaughter.