Attorneys general from more than 20 states have joined forces to investigate for-profit colleges that too often saddle students with crippling debt while furnishing them valueless degrees. The investigations have just begun. But it is already clear from testimony before a Senate committee that Congress must do more to rein in the schools and protect students.

For-profit colleges are typically more expensive than public colleges, which means students graduate owing more. They account for nearly half of student loan defaults, even though they enroll a little more than 10 percent of higher education students.

State prosecutors are uncovering unconscionable examples of fraud. Lisa Madigan, the attorney general of Illinois, testified this week that she had recently filed suit against a for-profit school that had saddled individual students with up to $80,000 in loans while promising employment with law enforcement agencies that do not recognize the school’s credentials as valid.

Jack Conway, the attorney general of Kentucky who leads the multistate group, has identified two schools that went bankrupt, leaving students with loads of debt and worthless credits and still on the hook for those outstanding loans.