Voters on Tuesday approved Edina Public Schools’ $125 million plan to renovate all of its schools, improve security, and add on to the high school, according to complete but unofficial election results.

With a vote of 57 percent in favor and 43 against, Tuesday’s vote was one of the narrowest margins of victory the school district has experienced in years.

School district leaders were nonetheless pleased with the outcome.

“We are very pleased that our community supported our plan and are looking forward to the next phase of partnering with our staff, students and their families,” said Susan Brott, the district’s communications director.

“The kind of changes we’re going to make in our learning spaces will have an impact on all of our students,” she said.

The heart of the district’s bond proposal calls for making widespread modifications to all Edina schools to create flexible learning spaces where students can work together in groups and teachers can switch seamlessly between working with students one-on-one and working with large groups. That part of the plan is expected to cost $100 million.

School leaders envision spaces within schools that function more like those in a modern office, with movable furniture, common work areas, spaces for large groups and areas where partitions could be easily erected or taken down.

The average age of Edina’s schools is 51 years, and district leaders argued that the bond proposal would help modernize those buildings.

The proposed project also calls for adding about 135,000 square feet at the high school, a plan being driven by the district’s plan to move ninth-graders from the middle school to create a more traditional high school and middle school experience.

Under the district’s plan, a multipurpose activities center would be built at the high school to accommodate physical education classes, to provide meeting spaces for extracurricular groups and to offer room for students to work on projects like robotics.

Under terms of the bond plan, the owner of a typical $400,000 Edina home would see an annual tax increase of $299 a year, according to preliminary cost estimates.

Construction would start in 2016.

Edina was one of 14 school districts with referendums on the ballot in May. Most school districts are asking taxpayers for money for renovations, though some are proposing an addition or money to build a new school.