ANDOVER — After serving as assistant principal for three years, Theresa McGuinness will take over as head of Doherty Middle School in July.

She replaces Bruce Maki, who is retiring after 20 years with the Andover school system.

"I've worked hard toward this, but I never expected it. I'm thrilled and honored to take on the position," McGuinness said. "It's a great school and community, a culture that values children."

McGuinness was one of two finalists out of a pool of 30 applicants. The other finalist was Kenneth Yee, assistant principal at Oak Hill Middle School in Newton.

Superintendent Claudia Bach made the announcement late last week, saying McGuinness was never a shoo-in as the internal candidate. It became clear she was the person for the job after interviews and feedback from parents, students and faculty, she said.

"Parents spoke of Ms. McGuinness' excellent communication and follow through and of her skill in dealing with difficult student issues," Bach wrote in a letter. "Students said they felt comfortable coming to her with issues that concerned them."

Bach praised her unique training in science, counseling and administration.

Before coming to Doherty, McGuinness was assistant principal at a Nashua, N.H., high school and headmaster of the Academy of Health and Human Services at that school. Prior to that, she held jobs as a guidance counselor in Stratham, N.H., and as a biology teacher in Nashua.

McGuinness received a bachelor's degree in microbiology from the University of New Hampshire. She has two master's of education degrees in secondary education and counseling from there as well.

Andover has seen a good deal of principal turnover this year.

South Elementary Principal Eileen Woods, West Elementary Principal Charles Friel, and Doherty's Maki will all retire in June. Denise Holmes left West Middle School in December, citing health problems. And last year, Stephen Jankauskas retired as Sanborn Elementary School's principal.

So far, three of the five open positions have been filled by Andover assistant principals. Jankauskas' job was filled by Patricia Barrett, an Andover native and former Andover teacher, who was working as a principal in Wakefield.

Bach is still looking for a replacement at South Elementary.