Children get dumber over the summer, says Peter Orszag, vice chairman of global banking at Citigroup Inc. and a former director of the Office of Management and Budget in the Obama administration.

He points to several research studies documenting the fade-out phenomenon, which is all well and good. Those of us of a certain age live with “fade out” every day. Concerning school children, whose brains still absorb new knowledge like sponges, it’s worth considering why they can’t seem to recall basics they allegedly learned about two months ago.

One explanation is that the time they do spend in school is not challenging enough. Surveys over the past several years have documented that students are bored silly.

Orszag’s preferred solution to summer fade out is more time in school. Of course, he’s not the only one suggesting this. But the evidence indicates quality school time trumps quantity seat time. Just look at our global competitors.

When it comes to time in school, top global performers prepare students in a fraction of the time and at a fraction of the cost compared to the United States. Among the 32 countries participating in the 2006 OECD PISA assessment, the United States had the most teaching hours per public school year, 1,080 compared to the international average of 803. Top international performers had far fewer teaching hours. Finland had 600 teaching hours, while the Republic of Korea had roughly 575 hours. Meanwhile, with 505 teaching hours per school year, Japan had the least teaching hours of all OECD assessment countries.

Those countries also spent significantly less than the U.S. but achieved superior results. U.S. cumulative spending per student between the ages of six to 15 was $80,000 and the average math scale score was about 475 out of a possible 1,000. Only Switzerland spent as much, but its students performed nearly 100 scale score points higher. Korea’s cumulative spending per student spending between the ages of six to 15 was around $40,000; Finland’s, around $50,000; and Japan’s was under $60,000. Still, students in each of those countries outperformed their American peers by 100 scale-score points or more. (See Chart B7.2)

This lack of productivity hurts students and our economy. Rather than fret over children’s two-month summer fade out, policy makers should be focusing instead on the apparent nine-plus months schooling system fade out.