Boston Mayor Marty Walsh says his plan to modernize the city’s aging school buildings also presents a chance to consolidate and make the system more efficient.

“If we were a business, someone would shut us down because it doesn't work,” Walsh said in an interview with WGBH News last month.

In Boston, there are some 20 different school configurations, from schools with only kindergarten and first grade to buildings spanning all grades. It’s expensive to run all of those buildings — more than 120 across the city — and employ principals or headmasters to lead them. The district is moving towards getting rid of middle schools and instead organizing campuses around either elementary or high school years.

“I'm not looking to cut money out of the school department,” Walsh said. “I'm looking to put more money into it.”

Boston is one of the few cities nationwide where the mayor oversees the school department and has the authority to appoint school committee members. Chicago is another. Even with wide influence over school policy, Walsh has struggled to advance some of his more ambitious ideas.

The mayor tried to create a one-stop registration process for charter and city schools in 2015. That didn’t pan out. Plans to create universal prekindergarten have been put on hold, since there’s no way to fund it. Walsh is now moving forward with his most ambitious plan — to spend $1 billion modernizing and consolidating schools.

So far parents, teachers and students aren’t happy with plans to close two high schools in June and a middle school in 2020.

“I know people are going to question the moves,” Walsh said. ”If they want every school to be good, then they have to allow us to do the very difficult decisions in order to make this district work.”

Walsh doesn’t have any projections for how much money could be saved if schools were more uniform in their grade-level structure, and it’s not clear how he’d reinvest the money in schools. Right now, about half of schools are underperforming. In ten years, Walsh said he wants the majority of the district’s schools to be high-performing.

The biggest obstacles to reaching that goal, according to Walsh, are the high cost of student transportation, poverty, inequality and poor housing. Many of those obstacles Walsh identified are external. To address them, the district needs to provide more services, he said. The city recently hired 20 psychologists and nurses to help kids suffering from trauma. To address hunger on campus, Boston built 30 school kitchens so staff could make fresh meals.

Boston City Councilor Annissa Essaibi George, a former Boston public school teacher who helps lead the city council’s education committee, offered a different take on challenges in the district. She said the district has underfunded an initiative to include special education students in mainstream classrooms across the district.

“That becomes a real problem, because all of the sudden you have a program that’s designed to have two or three adults in the classroom, now with only one adult in the classroom,” Essaibi George said. “Everyone loses.”

In September, the district agreed to add at least one teacher’s aide in so-called inclusion classrooms in 20 schools, after the Boston Teachers Union filed a complaint against the district with the American Arbitration Association.

Essaibi George said she doesn’t agree with all of the decisions made by the School Committee — or Walsh — and is exploring ways to change how schools are governed. That includes adding elected members to the committee or allowing the city council to choose some members.

It’s not clear whether Walsh would cede any of his power over schools.

Oakland, California, for example, has a hybrid school board with a mix of mayoral appointees and elected members, according to the Education Commission of the States. Boston School Committee members were elected until 1992, when a state law gave the mayor the power to appoint them.

Our coverage of K through 12 education is made possible with support from the Nellie Mae Education Foundation.