MADISON, Wis. -- Sexual predators across the nation are taking higher education classes at taxpayer expense even while they are locked up in treatment centers.

Critics said that they are exploiting a loophole to receive Pell Grants, the nation's premier financial aid program for low-income students.

Prison inmates are ineligible for grants under a 1994 law and so are students convicted of certain drug offenses, but sexual predators qualify once they are transferred from prison to state-run treatment centers.

U.S. Rep. Ric Keller of Florida said that it's the most insane waste of taxpayer money he's ever seen. He is sponsoring a plan to stop the practice.

Others said that taking away offenders' financial aid would be a mistake. They said that education could help sex offenders build stable lives if they are ever released.

Wisconsin and about 19 other states allow authorities to hold the most dangerous sex offenders for treatment after their prison sentences end.