The task of finding a replacement for the school system’s superintendent, Robert Maguire, who is leaving in June after 22 years with the district, is shifting into high gear. Residents have been chosen for the final seats on the search committee, which is slated to hold its first meeting Thursday. The district has set Friday as the deadline for applications; as of last week, 18 people had expressed interest in the position, and a total of 30 to 35 are expected to apply for the job. The School Committee hired Future Management Systems of Beverly to help locate and vet candidates. The search committee will winnow the field and recommend at least three finalists for the school board to consider, according to postings on the school district’s website, www.medfield.net.