Jeffrey Marsden, the superintendent of schools in Wrentham since 2006, has been chosen as the new leader of Medfield’s district, pending finalized contract negotiations. He would be replacing Robert Maguire, who is retiring on June 30 after serving as superintendent for 13 years, and working in the town’s schools for 22 years. Marsden holds a doctorate in education from Boston College. His first teaching position was in Taunton, and then worked several years in the Douglas school district as a fourth- and fifth-grade teacher, and then principal of Douglas Elementary School. The Wrentham district covers students in kindergarten through Grade 6, with the older students shifting to the King Philip Regional District. Marden will face new challenges in Medfield, which covers students through Grade 12. Wrentham’s School Committee members, who gave Marsden an A-plus rating for his work, have begun their search for his replacement.