GROTON — Taking the place of a popular school administrator is always difficult, and especially hard when the post being filled was held by Joseph Dillon. He was principal of Groton-Dunstable Regional High School for the past 12 years.

Such was the situation facing Holliston resident Shelley Marcus-Cohen, who was hired by the school district last spring to replace the departing Dillon.

Before being named as the district’s new high school principal, Cohen was the principal of the New Bedford Learning Charter School and a senior research fellow at the University of Massachusetts.

Dillon, meanwhile, had been given an emotional send-off at this year’s graduation ceremony, a sign of the deep regard with which he had been held by both students and faculty at the high school.

To ease the transition, Cohen said she spent the summer months acquainting herself with the district, its administration, rules and regulations, but declined to suggest any changes for the immediate future. Instead, she has decided to move slowly, instituting a new practice called “breakfast with the principal” as one way to continue learning about the school.

“The students have had another principal here for a very long time but we’re getting to know each other,” said Cohen. “And it’s getting better all the time. I’ve begun holding my weekly principal’s breakfast with two students from each grade. I invite the students to breakfast with me and we have coffee and donuts and bagels and I just get to meet the kids on a one-on-one basis. That way, I find out the things they love about the school and the things they would like to see changed. It’s a good way to meet the students and for them to meet me.”

Cohen said she spent the summer learning about the school district.

“I met with school Superintendent Alan Genovese several times, as well as with colleagues old and new, to get a feel for the district and to learn about the town as much as I could,” she said. “I’ve just sort of been familiarizing myself with the community. Also, I’ve been in the office catching up on the program of study here at the high school and studying the handbook.”

Such were her preparations that when the first day of school arrived last month, her presence in the principal’s office caused few ripples.

“It was wonderful, and continues to be so,” said Cohen. “I’ve been here for a couple of weeks now and at a concert this summer had a chance to meet some of the faculty and even some students.”

Dillon’s decision to resign his position last year did not come without some controversy, with some members of the faculty concerned about his reasons for leaving.

“I’ve been very well received by the faculty,” said Cohen. “They are an incredibly bright, talented and committed staff. They’re amazing and I thoroughly enjoy being with them. I’m learning from them as they are learning from me. So far, it’s been a great relationship.”

Cohen’s personal accomplishments include 18 years of teaching experience at the high-school level for Boston public schools, principal and assistant principal in Ashland and director of the Ashland Alternative High School. As a senior research fellow at the University of Massachusetts, Cohen taught courses in education and worked with area districts to provide state-of-the-art professional development opportunities to paraprofessionals, teachers and administrators.

Cohen holds dual master’s degrees from Boston University in educational media and technology and the University of Massachusetts in educational administration with specialization in supervision and evaluation. She is currently pursuing a doctorate in educational leadership, with a focus on curriculum and instruction, from Nova Southeastern University.

“Right now, I don’t really see any areas that need improvement,” said Cohen of the high school. “Any decision about things that are in need of improvement will come from the leadership team made up of administrators, faculty and students, as well as the School Council, whose members include parents, teachers and students. Right now, change is not on the agenda. This is a very successful school. People sometimes are afraid that a new administration is going to come in and rip things up but Groton-Dunstable Regional High School is a very successful school and I want to see that trend continue.”