FAIRFIELD — A decision as to the future size of Mill Hill School and its role in any potential redistricting may need to be made by June.

Part of the Board of Education’s approved recurring capital projects, the Mill Hill renovation and expansion is meant to address growing student enrollment and remove five existing portable classrooms, as well as bring the school up to date on fire, building and health codes, as well as federal American with Disabilities Act (ADA) compliance.

According to Fairfield Public Schools Executive Director of Operations Thomas Cullen, the total project could cost as much as $25 million — a figure that has increased in recent months and looms large in the minds of some members of the board.

“A month ago we were given a statement saying that a project that we’ve been told a year ago — not even a year ago — in August was going to be $18.7 million, is now possibly going to be as much as $25 million,” Board of Education member Jessica Gerber said at a Jan. 9 meeting of the board. “And just a year before that it was $15 million.”

At the Jan. 9 meeting, the board unanimously approved $1.5 million to form a building committee to carry out the project, though not without significant debate. The request will have to go through the Board of Selectmen, Board of Finance and Representative Town Meeting before the committee is officially formed. In order to apply to the state for reimbursement, the scope of the project must be decided by the end of June, Cullen said.

But, some board members, who will be tasked with hammering out the specifics of the project in that same time frame — including setting the future size of the school, which currently accommodates 378 students, though some members have speculated that it should be raised as high as 504 students — are worried they don’t have all necessary information.

“For the racial imbalance (plan), a redistricting plan is out there that, if memory serves, needed Mill Hill to be built to a 504 (capacity),” Board of Education member Christine Vitale said, citing a plan that would route more students to Mill Hill as part of a potential fix to lingering racial distribution issues in the district that defy state statute. She also noted that, according to consultant Milone & MacBroom’s enrollment projections, in order to possibly close a school after redistricting, Mill Hill needed to be built to accommodate 504 students.

She asked Cullen whether any money could be spent on research to better inform the board’s decision on the project in the coming months as they cement plans for the future of Mill Hill. According to Cullen, any money spent before a building committee is formed would have to come from the school district’s operating budget and would not be eligible for state reimbursement.

In agreement with Vitale, board member Jennifer Maxon-Kennelly said the board would be forced to make a “blind decision this spring” in terms of the potential addition to the school.

Others, like Chairman Philip Dwyer, urged quick approval, assuring the board that more detail would follow.

“Unless you spend $1.5 million to get all the answers you want, you won’t be able to make a decision because it is the collective team of all the development professionals that get you the information as to whether we’re talking about a $9 million project or a $20 million project,” Dwyer said.