Portland Public Schools needs voters to approve at least $257 million in new bonds to finish over-budget construction projects voters approved in 2017, and the district may ask for that cash on the November 2020 ballot.

But in addition to securing funding to finish the projects it had said would be paid for by the 2017 bond — remodels of Benson and Madison high schools and a total rebuild of Lincoln High and Kellogg Middle School — the school board must also decide when to ask voters to issue hundreds of millions more for projects in other buildings.

And if board members want to greenlight new construction with a 2020 bond measure, they have just six weeks to decide. A Jan. 17 meeting is their last chance to vote and place the measure on the November ballot.

The most important consideration for district staff, Chief Financial Officer Cynthia Le said, is ensuring the tax rate doesn’t top $2.50 per $1,000 of assessed value when Portland Public Schools asks voters to approve new construction.

To maintain that rate, Le said, board members could choose from two timelines.

Under the first, Portland Public Schools would ask voters for $893 million next year, then $549 million in 2024 and come back as needed every four years.

Or the school board could adopt an eight-year cycle and ask voters for $1.4 billion in 2020, $517 million in 2028, then again in 2036.

Another consideration in the bond development process, officials said, is how much staff time goes into crunching numbers and drafting plans. District officials are already working on several other projects, Le said, and adding bond development to that pile would further stretch central office staff.

The proposed school upgrades are part of a series of renovations, remodels and wholesale reconstructions the school board settled on about a decade ago.

Roosevelt, Franklin and Grant high schools received wholesale interior upgrades with the proceeds of a $482 million bond voters greenlit in 2012. Those projects came in around $4 million under budget, Le told the bond committee.

District officials had similar plans for Madison and Benson, while Lincoln High is slated to receive a total rebuild, under the $790 million bond voters passed in 2017. But those projects, which are largely still on the drawing board, have been plagued by overruns that put their total price tag at well over $1 billion.

The school board can decide to roll new construction into a bond to address those cost overruns as early as its Dec. 17 meeting, board Chair Amy Kohnstamm said. But Andrew Scott, who chairs the school improvement bond committee, told district staffers and board members on Thursday that a January meeting might make more sense.