DERRY — After an anticipated vote on a plan to close a school was derailed, school board members decided Tuesday to have a student population trigger that will set the wheels of closing a school in motion.

Before the meeting Tuesday night at West Running Brook Middle School, attended by about 50 residents, board chairman Lynn Perkins said he hoped to systematically go through each of the five options floated by administrators, narrow the options, amend as seen fit and vote on them.

But shortly after the meeting started, each board member explained their positions. No one wanted to vote on any of the options discussed for the past few months.

The board agreed to start the planning process for closing an elementary school after the student population declines to a certain level.

Some specific numbers were discussed but the board decided to figure out the details of the threshold at a later meeting.

Board member Dan McKenna suggested setting the threshold somewhere between 1,925 and 1,967 students in kindergarten through fifth grade. The number is based on an average class size of 21.6 students, 1,925 being 90 percent of capacity and 1,967 being 92 percent. Board member Erika Cohen suggested setting it at 1,871, which she calculated as 90 percent capacity based on an average class size of 21 students.

McKenna said enrollment is expected to reach 1,967 by the 2021-2022 school year. He said enrollment for K through 5 on Jan. 1 was 2,019.

The board has been considering closing a school as a cost saving measure for about four years, as enrollment started to decline.

Perkins expressed concern the board was being short-sighted about the financial burdens the district is facing down the road, saying they are possibly already living outside their means.

“We’re looking at $3 million of expenditures in the next four years,” Perkins said.

Perkins said he favored Options 1 or 4, which both present the most cost savings, estimated to be about $1 million by administrators.

Option 1 would have closed a school, converted one elementary school into an early education center with preschool and kindergarten, three elementary schools would house grades 1 through 4 and the two middle schools would house grades 5 through 8.

Option 4 would have closed a school, preschool would stay at Hood Middle School, four elementary schools would house K through 4 and the two middle schools would house grades 5 through 8.

McKenna said he favored Option 3, which would see a net savings of $429,000 as currently proposed, but would amend it so it would not require the use of portable classrooms, duplicate programs or negatively impact computer labs. Under the third option, one school would close, grades K through 5 would be housed at four elementary schools and the two middle schools would house grades 6 through 8.

McKenna would also like to move administrators to the closed school facility, lease the School Administrative Unit building and possibly gym facilities at the school to bring in revenue. He would also like to create a committee to look into other potential space uses for a closed school.

He said he wanted to use the savings from closing a school to fund tuition-free, full-day kindergarten and use the money from leasing the SAU building to accelerate the plan to have one computer for each student.

Board member Brenda Willis, who previously stated she was against closing any schools, said she didn’t disagree that the board needed to find a student per building ratio that would make closing a school necessary.

She said she is an advocate of closing the SAU building but not renting out space there.

Board member Erika Cohen said she personally prefers the same options preferred by Perkins, which are based on a grade 5 through 8 model. But she said she realized the public survey didn’t support those options, and she is a strong believer in answering to the public.

Board member Michelle McKinnon reiterated her position that she didn’t want to close any school.

“I’m going for Option 6,” McKinnon said. “Option 6 is sometimes the best chance is no change at all.”

Board member Paul Lutz said he had anticipated voting against the available options, but said he was in favor of setting a population trigger for returning to the issue of closing a school.

Board member Derick Anderson said he prefers whatever option administrators say is best for the students. While he thinks the enrollment trends have appeared to have leveled out, he said he was in favor of finding a number that the board agrees is “a floor.”

Both McKenna and Cohen said they favored closing Grinnell Elementary School. Cohen said it would have the added benefit of “socioeconomic integration.”

Perkins said he didn’t want to discuss which school would be closed at this meeting.

Some members of the public spoke after the vote. One resident said they didn’t want to see the board box itself in by deciding to close a school in case new development causes enrollment to grow again.

Resident and former town councilor Paul Needham said he supports the plan to close a school because the money saved from that will be used where it needs to be used.