Employment among 16-to 19-year olds in May grew by just 6,000, the smallest increase since 1969, when teen jobs fell by 14,000, according to government data analyzed by employment firm Challenger, Gray & Christmas. In May 2008 and 2009, teen employment grew by over 110,000.

“It’s certainly a preliminary strong indication that it’s going to be a tough job market for teens,” said John Challenger, CEO of Challenger, Gray & Christmas.

Jobs traditionally given to teens are apparently going to older workers who are willing to take low paying job to make ends meet. Employment among 20- to 24-year-olds grew by 270,000 in May, an unusual spike, considering that employment in the same age group fell by 261,000 in May 2009.

"Also impacting the job market for young adults are the large number of older adults who are willing to accept even a temporary, seasonal position simply to generate some income," said Steven Rothberg, chief executive officer of CollegeRecruiter.com, an online entry-level job-posting site.

"We're seeing experienced candidates taking jobs normally reserved for college grads and college grads taking jobs normally reserved for college students," said Rothberg.

But there's still a possibility for a turnaround, Challenger said, since June is traditionally the month when employers do the majority of their summer hiring. A strong June or July could still lift total hiring for the season, even if it looks unlikely now.

Another reason for slower hiring, experts said, is that the establishments that usually add summer help are also the places where Americans hit by the recession may be cutting back on spending. The majority of young Americans aged 16- to 24-years old worked in the leisure and hospitality industry last year at establishments such as theme parks, hotels and restaurants. The other popular industries were in retail and in education and health services, according to the Bureau of Labor Statistics.

Employers may prefer the older workers, experts said, because they get a more experienced employee for their money.

“They feel like they get someone who's more mature," said Challenger, "and has better work habits, no question."