The Association of California School Administrators is the largest umbrella organization for school leaders in the United States, serving more than 18,000 California educators, and its top priority is advocating for public school students in kindergarten through grade 12.

Addington began his career in education as a school psychologist with the Fresno County Office of Education in 1990, moving the next year to the Hanford Elementary School District. In 1998, he became Assistant Principal and District Coordinator of Special Ed with Central Union School District. He served as Assistant Superintendent from 2002-2012, when he became Superintendent of the district. 

The Central Union District (CSUD) consists of four schools, two of which, Admiral Akers School and R.J. Neutra School, are located on Lemoore Naval Air Base, along with Stratford School and Central School.

Jeffrey Gilcrease, CUSD Board President, said, "Central Union School District has four schools with quite a diverse population ... children from agricultural areas ... military families ... and an Indian Reservation. Tom has met this challenge with skill and grace."

Understanding the importance of voicing what is needed to guarantee success of all students beyond the walls of the district, Addington has maintained a positive political connection at the local, state and federal level. He is a member of the executive leadership board for the Central Valley Education Coalition (CVEC) ensuring that the needs of Valley students are kept at the forefront.

He has been an active member of ACSA at the charter, regional and state levels, most recently serving as vice president of legislative action for Region XI. Overseeing the education of military and Native American students, Addington is a member of the Military Impacted School Association (MISA) and the National Association of Federally Impacted Schools (NAFIS), as well as the California Association of Federally Impacted Schools (CAFIS) where he currently serves as a board member.

ACSA stated that Addington is a committed, visionary, educational leader who believes the most important component of a strong administrator is to provide an open, inviting climate that encourages individuals to freely share their thoughts and concerns regarding educational issues. He leads the Central Union School District by entrusting every employee to empower every student to excel to his or her highest potential.