Washington -- As the financial meltdown and economic slump hold the national spotlight, another potential crisis is on the horizon: a persistently high dropout rate that educators and mayors across the country say increases the threat to the country's strength and prosperity.

According to one study, only half of the high school students in the nation's 50 largest cities are graduating in four years, with a figure as low as 25% in Detroit. And while concern over dropouts isn't new, the problem now has officials outside of public education worried enough to get directly involved.

The U.S. Conference of Mayors is focusing its education efforts on dropouts. Mayors in Houston and other Texas cities go door to door to the homes of dropouts, encouraging them to return to school. Atlanta Mayor Shirley Franklin meets on weekends with students and helps them with life planning. Other cities, like Milwaukee and Kansas City, Mo., have dropout prevention programs.

Some new studies show far fewer students completing high school with diplomas than long believed. "Whereas the conventional wisdom had long placed the graduation rate around 85%, a growing consensus has emerged that only about seven in 10 students are actually successfully finishing high school" in four years, said a study by the Editorial Projects in Education Research Center, a nonprofit group based in Bethesda, Md. It was released this year by America's Promise Alliance, a nonpartisan advocacy group for youth. In the nation's 50 largest cities, the graduation rate was 52%.

The longstanding American dropout problem may be especially thorny now, with a looming recession. Cutting the number of dropouts in half would generate $45 billion annually in new tax revenue, according to America's Promise -- assuming there are ultimately enough jobs to accommodate the graduates.