The Organization for Economic Cooperation and Development places the United States 18th among the 36 nations examined, USA Today reported Wednesday.

Headed to the top of the heap is South Korea where 93 percent of high school students graduate on time compared with the United States where 75 percent receive their diplomas.

The seemingly downward trend of U.S. education worries economists.

"The United States has rested on its laurels way too long," Jacob Funk Kirkegaard of the Peterson Institute for International Economics in Washington, told USA Today. "Other countries have increasingly caught up and surpassed the United States."

"We've been asleep for a good number of years as a country," says Richard Freeman, an economics professor at Harvard. "It's not that we're doing horrible. But the other guys are moving faster."