Kristine Nash, Hanover’s superintendent of schools for six years, will retire on Nov. 2 after 45 years in education. Nash was hired in 2006 to replace Superintendent Mary Ann Jackman, who resigned. She previously worked in the Dover-Sherborn public school district, as well as in East Bridgewater and Marshfield. When Nash renewed her contract with the Hanover School Committee in 2009, she said she would stay for as long as it took to get the new high school up and running. The new school opened in September, and students have completed a full school year. Nash submitted her letter of resignation on Aug. 1, and school officials say they expect to start looking for a successor immediately.