Four years in college and decades in debt—is it worth it?

With college graduates struggling to find full-time employment, future students should consider alternatives to a four-year college degree, said a former secretary of education.

"Fifty percent of our college graduates are ether unemployed or underemployed," William Bennett, who was education secretary under President Reagan, told CNBC's "Closing Bell."

"It used to be almost automatic that the advice would be, 'Go to college.' Now I think people have to pause and consider very carefully," he said, adding that there are other ways to achieve success.

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A two-year degree can be a less expensive and more effective path for some, and open online courses can provide marketable skills for much less than college, he said.

Student loan debt is currently estimated at $1.2 trillion.

By CNBC's Anna Andrianova. Follow her on Twitter @AndrianovaAnna.