They've shared a campus for decades. Soon they'll share a principal and teachers.

Hamilton-Wenham Regional School District Superintendent Marinel McGrath told School Committee members this week Miles River Middle School will merge with the high school, effective in July.

The search for a replacement for departing High School Principal Robert Krol has been suspended, McGrath said, and current Middle School Principal Matthew Fox will assume control of both schools. The current assistant principals in each school, Philip Conrad and Christy Reynolds, will assist Fox.

The move is intended to save money and improve efficiency. Krol made $106,730 in 2007. Administrators are touting educational benefits as well.

The district will become the only one on the North Shore to have a single principal for the middle and high schools.

"I haven't come to this decision lightly," McGrath said. "The teachers will have to look at themselves in a different way."

Both schools will operate on the same schedule, eliminating a five-minute difference in opening bells. This year there are 511 students enrolled in grades six through eight, and 715 in grades seven through 12.

Committee member Don Gallant asked whether the change would have educational benefits.

McGrath said she believes it will help keep class sizes small if the two schools share teachers. An accredited high school teacher can teach one middle school class, and a middle school teacher can teach one high school class.

"I also envision it will help us maintain the greatest number of programs," McGrath said.

Some middle school students might be able to accelerate their education by taking high school courses, she said.

Despite all the benefits, McGrath admitted there will be some culture shock, with each entity feeling as though it is losing a bit of its identity, but that can and will be overcome.

"We're professional educators, we have the creativity and we have the skills to make this work," she said.

One of the biggest casualties of the change will be the team teaching method adopted by the middle school several years ago.

Committee member Denise Bisaillon said that while she was a proponent of team learning, she supported restructuring.

"It's a very creative decision," Bisaillon said, "and very courageous."

Fellow board member Jack O'Keefe concurred.

"As desirable as the team model is, we can't sustain it economically," O'Keefe said.