As school districts scout ways to engage students already accustomed to instant messaging and interactive video games, they’re buying up the kind of tech tools once reserved for jet-setting corporate executives. Educational sales of personal digital assistants, laptop computers, and handheld remote controls called “clickers” are ballooning nationwide. Last year, a survey by Quality Education Data Inc. found that 28% of U.S. school districts offered handhelds for student and teacher use. One of every four computers purchased by schools was a laptop. One of the frontrunners was Yankton High School in South Dakota, which adopted Palm handhelds in 2001 and found they improved students’ grades.