After graduating, Hagar studied theology under
John Williams in
Schenectady, New York. In 1844 he was appointed superintendent of schools in
Canajoharie, New York and principal of the Canajoharie Academy. From 1852 to 1865 he served as headmaster of
The Eliot School in
Jamaica Plain. In 1857, Hagar attended the first meeting of what would become the
National Education Association and wrote the organization's original constitution. In 1865, Hagar was appointed principal of the Salem Normal School (now Salem State University). During Hagar's tenure as president, the school expanded and renovated its building due to increased enrollment, expanded its curriculum, and developed a plan for a new school building that would include a training school for normal school students. In 1884, Hagar served as a Republican
presidential elector for
Massachusetts's 7th congressional district. He was chosen after poet
John Greenleaf Whittier declined. Hagar died on July 4, 1896, in
Sharon, Massachusetts. ==References==