School buildings are costly to construct, yet too many of them sit idle and unused too much of the time. In addition, American students are falling behind their peers in other industrialized nations who spend longer hours each day, and more days in the classroom.

It would seem possible to attack both those problems at once by lengthening the school day and the school year. It makes no sense for youngsters during their crucial education years to spend more days out of the classroom than they spend in it.A new study by a congressional subcommittee notes that U.S. students have a 180-day school year and a comparably short school day. Most advanced countries have longer school days, and school years in those nations last up to 240 days. American students can fall as much as a year behind their foreign counterparts during one long summer vacation.

Some efforts have been made in Utah and elsewhere to better utilize buildings by going to a year-round schedule. This reduces long vacation absences and keeps the building occupied most weeks, although it doesn't lengthen the 180-day school year for students.

But those experiments have been confined so far to elementary schools. The vastly bigger and far more expensive high schools still stand relatively vacant all summer.

Yet any attempt to go on year-round schedules with high schools poses a myriad of problems, as a study in the Jordan School District showed this week. At the very least, it would mean a drastic lifestyle change for students, families, and teachers. And while it would increase building capacities by a third - thus reducing the need for new high schools - more money would have to be spent to hire more teachers.

The study notes that such scheduling is not expected for at least five years and would only be used as long as enrollments kept climbing. Once enrollment levels dropped, the traditional school format could be resumed.

But what is so sacrosanct about the current 180-day schedule? This is no longer an agrarian society that needs youngsters at home to work on the farm. As the congressional study noted, that kind of school year is doing a disservice to American youth - they are not being educated as well as youngsters in other countries.

School buildings are an expensive resource that ought to be used year-round, instead of being allowed to stand idle. And the best way to use them is to have students in them, being taught.

This has nothing to do with crowded conditions or high enrollments. It simply makes good sense, no matter how many students are involved.