One fast-growing American industry has become a conspicuous beneficiary of the recession: for-profit colleges and trade schools.

At institutions that train students for careers in areas like health care, computers and food service, enrollments are soaring as people worried about weak job prospects borrowaggressively to pay tuition that can exceed $30,000 a year.

But the profits have come at substantial taxpayer expense while often delivering dubious benefits to students, according to academics and advocates for greater oversight of financial aid.

Critics say many schools exaggerate the value of their degree programs, selling young people on dreams of middle-class wages while setting them up for default on untenable debts, lowwage work and a struggle to avoid poverty. And the schools are harvesting growing U.S. government student aid dollars, including grants awarded to low-income students.

‘‘If these programs keep growing, you’re going to wind up with more and more students who are graduating and can’t find meaningful employment,’’ said Rafael I. Pardo, a professor at Seattle University School of Law and an expert on educational finance. ‘‘They can’t generate income needed to pay back their loans, and they’re going to end up in financial distress.’’ For-profit trade schools have long drawn accusations that they overpromise and underdeliver, but the woeful economy has added to the industry’s opportunities along with the risks to students, according to education experts.

They say these schools have exploited the recession as a lucrative recruiting device while tapping a larger government pool of student aid.

‘‘They tell people, ‘If you don’t have a college degree, you won’t be able to get a job,’’’ said AmandaWallace, who worked in the financial aid and admissions offices at the Knoxville, Tennesse, branch of ITT Technical Institute, a chain of schools that charges $40,000 for two-year associate degrees in computers and electronics.

‘‘They tell them, ‘You’ll be making beaucoup dollars afterward, and you’ll get all your financial aid covered.’’’ Ms.Wallace said she left her job at ITT in 2008 after five years because she was uncomfortable with what she considered deceptive recruiting, which she said masked the likelihood that graduates would earn too little to repay their loans.

A spokeswoman for the school’s owner, ITT Educational Services, Lauren Littlefield, said the company had no comment.

The average annual tuition at forprofit schools this year is about $14,000, according to the College Board. The forprofit education industry says it is fulfilling a vital social function, supplying job training that provides a way up the economic ladder.

‘‘When the economy is rough and people are threatened with unemployment, they look to education as the way out,’’ said Harris N. Miller, president of the Career College Association, which represents 1,400 such institutions.

‘‘We’re preparing people for careers.’’ For-profit schools have long derived the bulk of their revenue from U.S. government loans and grants, and the percentages have been climbing sharply.

The Career Education Corp., a publicly traded global giant, reported revenue last year of $1.84 billion. About 80 percent came from U.S. loans and grants, according to BMO Capital Markets, a research and trading firm. That was up from 63 percent in 2007.

The Apollo Group, which owns the for-profit University of Phoenix, derived 86 percent of its revenue from U.S.

student aid last year, according toBMO.

Two years earlier, it was 69 percent.

For-profit schools have proved adept at capturing money from the government program called Pell grants, which are a centerpiece of the administration’s efforts to make higher education more affordable.

Two years ago, students at for-profit trade schools received $3.2 billion in Pell grants, according to the Department of Education, less than went to students at two-year public institutions. By the 2011-12 school year, the administration now estimates, students at for-profit schools should receive more than $10 billion in Pell grants, more than their public counterparts.

Enrollment at for-profit trade schools expanded about 20 percent a year in the past two years, more than double the pace from 2001 to 2007, according to the Career College Association.

Mr. Miller, the association’s president, said for-profit schools were securing large numbers of Pell grants because their financial aid offices were diligent and because the schools served many low-income students.

But financial aid experts say the surge of government money reaching such institutions reflects something else: their aggressive, sometimes deceitful recruiting practices.

Jeffrey West was working at a pet store near Philadelphia, earning about $8 an hour, when he saw advertisements for training programs offered by WyoTech, a chain of trade schools owned by Corinthian Colleges, a publicly traded company that reported revenue of $1.3 billion last year.

After Mr. West called the school, an admissions representative drove to his house to sell him on classes in auto body refinishing and upholstering technology, a nine-month program that cost about $30,000.

Mr. West blanched at the tuition, he recalled, but the representative assured him the program amounted to an antidote to hard economic times.

‘‘They said they had a very high placement rate, somewhere around 90 percent,’’ he said. ‘‘That was one of the key factors that caused me to go there.

They said I would be earning $50,000 to $70,000 a year.’’ Fourteen months after he completed the program, Mr. West, 21, has failed to find an automotive job. He is working for $12 an hour weatherizing foreclosed houses.

With loan payments reaching $600 a month, he is working six and seven days a week to keep up.

Corinthian says it bars its recruiters from making promises about pay.

‘‘The majority of our students graduate,’’ said a spokeswoman, Anna Marie Dunlap, in a written statement. ‘‘Most see a significant earnings increase.’’