Americans are flooding the government with appeals to have their student loans forgiven on the grounds that schools deceived them with false promises of a well-paying career—part of a growing protest against years of surging college costs.

In the past six months, more than 7,500 borrowers owing $164 million have applied to have their student debt expunged under an obscure federal law that had been applied only in three instances before last year. The law forgives debt for borrowers who prove their schools used illegal tactics to recruit them, such as by lying about their graduates’ earnings.

The U.S. Education Department has already agreed to cancel nearly $28 million of that debt for 1,300 former students of Corinthian Colleges—the for-profit chain that liquidated in bankruptcy last year. The department has indicated that many more will likely get forgiveness.

The program could prove to be one of the few lifelines for hundreds of thousands of Americans buried in student debt after attending disreputable schools that failed to land them a decent job. Federal law prohibits student debt from being discharged in bankruptcy, except in rare circumstances, and the Supreme Court last week declined to hear a case that could have expanded bankruptcy options.

The sudden surge in claims has flummoxed the Education Department, which says the 1994 forgiveness program is overly vague. The law doesn’t specify, for example, what proof is needed to demonstrate a school committed fraud. Last week, the department began a monthslong negotiation with representatives of students, schools and lenders to set clear rules, including when the department can go after institutions to claw back tuition money funded by student loans.