The war over whether the Upper Darby School District can build a $60 million, 950-student middle school in Clifton Heights at the site of popular ball fields that some residents call the “Field of Dreams” is escalating.

Clifton Heights officials are pushing changes in the borough’s zoning ordinance that could prevent or slow down the district’s plans to build a school on the municipality’s last nugget of open space, and also require new environmental and traffic-impact studies for such a project. The borough council is slated to vote on the moves May 28.

In response, the Upper Darby school board is racing to hold an emergency meeting Monday night to cancel the borough’s lease on the district-owned property and speed up the process to begin applying for permits to build the new middle school in the 6,500-person borough. On Thursday borough solictor Francis J. Catania sent a letter to the district calling its hurried attempt to terminate the lease “vindictive” and threatening legal action.

“We’ve been trying and trying to fight fair and they have not — we can’t do it anymore,” said superintendent Daniel McGarry. Board members in Delaware County’s largest school district had been poised to cancel the lease last month but held off after as many as 500 Clifton Heights residents staged a protest at the field.

Clifton Heights Mayor Joseph Lombardo insisted that the borough had already been in the process of modernizing its zoning code before Upper Darby unveiled its plan to build the new middle school, but he also struck a defiant tone about the controversial project, which is targeted for a 2023 opening.

“We’re going to do everything in our power to save our fields, because that’s what our citizens want,” Lombardo said. “If we have to take legal action we’ll certainly do that.”

The showdown has pitted educators who are desperate to relieve chronic overcrowding in Upper Darby’s two existing middle schools and insist Clifton Heights is the best geographic site for a third one, against borough residents who say a 150,000-square-foot school will wreak havoc with popular events like fireworks or the Boys Clubs’ annual Cow Pie Bingo now staged at the field.

McGarry insisted the district will eventually reach agreements to allow community groups like the Boys Club and the Police Athletic League to continue using the site, on North Springfield Road, near South Church Street. The district says the completed school will include a multipurpose football-size field, four baseball diamonds, two short-size soccer fields, and an indoor gym that residents and community groups can use when school is not in session.

By voting to cancel the borough’s current $1-a-year lease on the land it acquired when merging with Clifton Heights’ former school district in the 1970s, and by officially launching the project, Upper Darby officials believe that any zoning changes approved by the borough later this month won’t apply to the school. District officials said they weren’t informed of the changes but learned of them when school officials saw a legal ad in a newspaper.

“Once [the school project] goes on record, it would potentially block those ordinances,” McGarry said. He said the district and its lawyers believe the current ordinance would apply if the clock on the project begins with Thursday’s vote.

“[If] they continue to put up legal hurdles in front of us, it will end up playing out in court,” the superintendent said. “We believe the law is on our side if we go.”

Upper Darby school board president Rachel Mitchell said the board was forced into the emergency vote. “We have to act now on this issue,” she said in a statement, “but will continue to engage all parts of the community on an ongoing basis regarding decisions surrounding this property.

“I think they’re crazy,” countered Lombardo, the mayor, who said the borough has been working to update its zoning ordinance since January 2018 — several months before the first discussions of the proposed middle school — and that the moves were inspired by other development plans for several large tracts in Clifton Heights.

The proposed zoning-ordinance changes also include requiring impact statements for how projects would affect the environment, traffic, borough finances and the surrounding community. “In my opinion there’s nothing that we’re changing that can keep them from building a school there. ... Is it going to be on the timetable they want it to be? I don’t know.”