ANNANDALE-ON-HUDSON, N.Y.— As Congress considers President Bush's plan for new national accountability in public education, one proposal being embraced by politicians with responsibility for the schools -- as well as by a public clamoring for better performance -- is lengthening the time children spend in school. Gov. Gray Davis of California wants to extend the school year by 30 days for some children. Mayor Rudolph Giuliani calls for weekend classes in science.

Countries whose children outperform ours on international tests have longer school years, the argument goes, and therefore our children should spend more time in school.

The facts, however, tell a different story. It is not the aggregate time spent in school that accounts for the differences in performance, but how the time is spent.

Three countries whose eighth graders outperform America's in basic subjects are Korea, Canada and France. The school year in Korea has 220 days, compared to 178 in the United States, but Korean students get fewer hours of formal instruction each day. Canada, too, has a longer school year (by 10 days) but fewer hours of daily instruction. France has a school year precisely as long as ours, but with substantially more hours of instruction in key areas.

The common-sense conclusion is that the deciding factor in learning is not how much time is spent in school but the quality of the hours devoted to classroom teaching.

We waste too much of our children's time. In the last four years of American schooling -- high school -- pupils study the core subjects of mathematics, science, history, the national language and literature for less than half the time French and Japanese students do. Only 41 percent of the American high school day is spent this way. It should come as no surprise that a 1999 study financed by the Education Department, ''Is It Just a Matter of Time?'' concluded that it is the quality of education time that is the critical determinant of how much students will learn.

Lengthening school time as it is now utilized might even lower achievement. American students are falling behind because they are bored and poorly taught. Making them stay longer in the institutions that are failing them extends a form of incarceration that will only further depress the motivation to learn.

Another issue is who is doing the teaching. In all the countries that outperform us in math and science, from Singapore to Russia, a higher percentage of teachers has extensive training in the subject matter they teach. Their degrees are not in that amorphous field called education. A 1996 Education Department survey revealed that the majority of American math and science teachers do not have academic degrees in math or science. These teachers are entirely dependent on state-mandated, second-rate textbooks and teaching manuals.

As for the sudden popularity of the idea of extending school hours, the reasons are more social than educational. Governor Pataki's championing of a longer school day with an emphasis on after-school enrichment programs is at least honest in that it does not pretend to offer a solution to poor academic performance. Given the number of working parents and the absence of constructive alternatives in the late afternoon and early evening, after-school programs focusing on the arts, sports, technology, community service and other activities would be an important and long overdue investment; needless to say, children need alternatives to the street and television.

And the benefits of such programs to the development of motivation, creativity and self-esteem are well-documented. Children need independent, rigorous and engaging activities not only after school, but also during the summer. But merely extending activities mishandled during the school day would only prolong emptiness and waste.

The money that politicians would use to keep schools open longer should instead address the true causes of other countries' superior performances: recruitment and training of effective teachers, a focus on basic academic subjects and high standards for classroom materials. Only when we have 178 school days that function well should we consider what to do with the rest of children's time.

Drawing (Jordin Isip)