Arlington Public Schools plans to distribute a MacBook Air laptop computer to every ninth grader at three high schools this year, school officials said.

The laptops are one of many pilot programs in the county’s school system as it pursues a goal of giving every student a computer by 2017.

Arlington officials say that one-to-one computing could transform teaching and reduce the achievement gap by giving students access to personalized instructional materials around the clock.

Many school districts around the country are moving in this direction, particularly as standardized tests — and more textbooks — move online.

Last spring, the push for personal computers in Arlington was the subject of debate among school board members and teachers, many of whom are uncomfortable making technology a central part of the classroom. A proposal by superintendent Patrick K. Murphy to spend $200,000 to provide a tablet computer to every second- and sixth-grader was removed from the budget.

But Rajesh Adusu­milli, assistant superintendent for information services, said that the goal has not changed.

Every school in Arlington has a pilot program with one-to-one computing in at least one classroom, he said. Through the pilot programs, the district hopes to learn more about how best to use the devices as they seek to use them on a broader scale.

Teachers are experimenting with the computers in different ways. Some are videotaping lessons their students can watch at home; others are sending students e-books selected for their particular reading levels or assigning projects that students can work on together through on-line networks.

The laptops themselves cost about $1.2 million and were paid for with funds already allocated for computer replacement in the budget, Adusumilli said.

They will go to freshmen at Wakefield, Washington-Lee and Yorktown high schools. Another pilot is being planned for HB Woodlawn.

The high school students will not be able to take the computers home right away, Adusumilli said. Teachers and students will need to get comfortable with them at school first and learn how they can be used to support instruction.