The Arlington School Board gave unanimous approval Tuesday to a building plan that includes construction of the county’s first new schools in more than a decade, part of a long-term effort to keep pace with skyrocketing enrollment.

The 10-year, $538 million capital-improvement plan, passed after months of community meetings and work sessions by the board, calls for two new elementary schools as well as classroom additions at three elementary schools by 2017.

It also sets aside money to add an additional 3,000 seats between 2016 and 2020, mostly at the middle- and high-school levels.

The student population is booming across much of Northern Virginia, and school systems, including those in Loudoun and Fairfax counties, are well practiced in the planning and construction of new facilities. But Arlington, a smaller and more densely developed county, hasn’t built a new school since Carlin Springs Elementary was completed in 2001.

More than a dozen schools in the county are already bursting at the seams, and the entire school system is projected to be over capacity by the 2013-14 school year.

“In the past, our focus has been on renovation and renewal,” schools spokeswoman Linda Erdos said. “In this and in future [capital improvement plans], we expect the board will continue to look at any renewal needs that we have, but the emphasis clearly is going to be on building capacity.”

Arlington’s overall population has grown the past decade, boosted by the construction of thousands of apartments and other multifamily units. School enrollment has increased more than 18 percent in the past four years and is now about 22,700. That’s expected to approach 27,000 by 2017.

The new elementary schools will each house 600 students. One will be a neighborhood school on the Williamsburg Middle School site in the northern part of the county, which is particularly crowded, and is set to be completed in 2015.

The other will be built in a more central location — on the campus that is currently home to Kenmore Middle and Carlin Springs Elementary schools — and will house a yet-to-be-determined program that will draw students from across the county. It will be completed in 2017.

The additions at three elementary schools, of 12 classrooms each, will expand the number of seats at Arlington Traditional School, Ashlawn and McKinley. The school system will also upgrade infrastructure at schools across the county.

Funding will come largely from capital reserves and bond sales. The board passed a resolution Tuesday calling for a $42.6 million bond referendum, to be voted upon in a fall special election. That request now goes to the Arlington County Board.

Soon, the school board will turn its attention to deciding how boundaries for elementary and secondary schools should be adjusted.

Any boundary changes probably wouldn’t take effect until the new schools open, Erdos said, but “the board would like to give families as much notice as possible.”