The Portland Board of Public Education has tasked its District Advisory Building Committee with finding a way to finish renovations to four elementary schools in the face of rising construction costs.

The school district said that finishing a scaled-back renovation at the four schools would cost $21 million more than the $64.3 million bond city voters approved in 2017.

The board considered three options during a workshop Tuesday night, but no decision was made.

Option one would involve reducing the scope of renovations to the Lyseth, Longfellow, Reiche and Presumpscot elementary schools. Under that option, the school district would still need to come up with roughly $21 million more than the $64.3 million “Buildings for our Future” bond approved three years ago.

Another option would be to renovate two of the four schools. One of those schools would be Lyseth, where renovations have already begun. Lyseth renovations are scheduled to be completed in 2021.

The third option would be to seek increased funding to renovate all four schools as envisioned by voters when the bond was approved.

In 2017, voters overwhelmingly approved the $64.3 million bond. A competing bond measure calling for borrowing $32 million to renovate only the Lyseth and Presumpscot school was defeated in 2017. The smaller bond was supported by residents who favored waiting to see if the state would pay for renovating or replacing the Reiche and Longfellow elementary schools.

The District Advisory Building Committee will meet at 6 p.m. Thursday at the district offices at 353 Cumberland Avenue. The board said it could accept or reject the committee’s recommendations.

Timothy Atkinson, a board member, urged his colleagues to act swiftly or face a further escalation in construction costs.

The issue of renovating city elementary schools has been discussed for more than two decades. Many of the schools were built more than 40 years ago and are in need of being modernized.

The district plans to seek bids on the remaining school renovation projects this fall.

This story has been updated to reflect that the District Advisory Building Committee meeting will be held at the school district offices at 353 Cumberland Ave.