SOUTH PORTLAND — The Board of Education voted Monday to approve a contract with PC Construction of Burlington, Vt., to renovate and expand the city’s high school under a plan that will reduce the cost of the project by about $4 million.

PC Construction submitted the low bid of $43.2 million for the project. That price was $4 million more than the $39.2 million bond for the project approved by South Portland voters in 2010.

The School Department negotiated a lower price, which was accepted by the school board. The contract will go to the City Council on Wednesday night for final approval.

Ralph Baxter, chairman of the South Portland High School Building Committee, said most of the cost reductions were made by simplifying the interior and exterior designs of the building.

Committee members incorporated more metal siding, instead of brick, into the design, reduced window sizes, simplified floor tile designs and left the basement of the Beal Gym intact to save money.

“We had to make some tough choices but were able to reduce the budget without compromising the integrity of the building,” Baxter said.

The renovation is expected to be completed by December 2014, with construction expected to start this spring.