WASHINGTON (AP) ― Once a rite of passage to adulthood, summer jobs for U.S. teens are disappearing. Older workers, immigrants and debt-laden college graduates are taking away lower-skill work as they struggle to find their own jobs in the weak economy.

Fewer than three in 10 American teenagers now hold jobs such as running cash registers, mowing lawns or busing restaurant tables from June to August. Employment for 16-to-19-year olds has fallen to the lowest level since World War II over the past decade.

And teen employment may never return to pre-recession levels, a projection by the U.S. Bureau of Labor Statistics suggests.

The drop is partly a cultural shift. More teens are spending summer months in school or at camps preparing for college. But the decline is troubling for teens for whom college may be out of reach.

Upper-income white teens are three times as likely to have summer jobs as poor black teens, sometimes capitalizing on their parents' social networks for help.

Overall, more than 44 percent of teens who want summer jobs don't get them or work fewer hours than they prefer.

``It's really frustrating,'' said Colleen Knaggs. The 18-year-old graduated from high school last week in Arizona, the state that ranks highest in the share of U.S. teens who are unable to get the summer work they desire, at 58 percent.

Wanting to save for college, Knaggs says she submitted a dozen applications for summer cashier positions. She'll be babysitting her 10-year-old brother instead.

``I have big concerns about this generation of young people,'' said Harry Holzer, labor economist and public policy professor at Georgetown University. He said the income gap between rich and poor is exacerbated when lower-income youths who are less likely to enroll in college are unable to get skills and training.

``For young high school graduates or dropouts, their early work experience is more closely tied to their success in the labor market,'' he said.

Washington, D.C., was most likely to have teens wanting summer work but unable to get it or working fewer hours than desired, with more than three in five in that situation. It was followed by Arizona, California, Washington state, Florida, Tennessee, North Carolina and Nevada.

On the other end of the scale are Wyoming, North Dakota, Oklahoma, Nebraska, South Dakota and Kansas. All have fewer immigrant workers.

About 5.1 million, or just 29.6 percent, of 16-to-19 year olds were employed last summer. In 1978, the share reached a peak of nearly 60 percent before waves of immigration brought in new low-skill workers. Teen employment remained generally above 50 percent until 2001, dropping sharply to fresh lows after each of the past two recessions.

By race and income, blacks, Hispanics and teens in lower-income families were least likely to be employed in summer jobs.

Out of more than 3.5 million underutilized teens who languished in the job market last summer, 1.7 million were unemployed, nearly 700,000 worked fewer hours than desired and 1.1 million wanted jobs but had given up looking.

The figures are based on an analysis of Census Bureau Current Population Survey data from June to August 2011 by Northeastern's Center for Labor Market Studies. They are supplemented with research from Christopher L. Smith and Daniel Aaronson, two Federal Reserve economists, as well as interviews with Labor Department economists and Challenger, Gray & Christmas, a national job placement firm.

Smith, the Fed economist, attributes at least half of declining teen employment since the mid-1980s to youths who are being crowded out of the job market by older workers and immigrants.

According to government projections, the teens entering the U.S. labor force are expected to decline another 8 percentage points by 2020. Much of the recent employment decline is due to increased competition from other age groups for entry-level jobs that teens normally would fill.