They’ve done the crime, now they are doing the time, and some are doing less for hitting the books. The students are prison inmates, some of the toughest in Indiana.

"I'm receiving a business degree (search) and I'm also working toward a bachelors in liberal arts," said inmate Bryan Pierce.

Prisoners who attend the school behind bars earn more than diplomas — they earn time off their sentences. A bachelor's degree cuts two years off a sentence, an associate's degree is worth one year and a vocational class deducts three months. The rules have been in effect since a state law was passed in 1993.

Diane Wheatley, who was raped ten years ago, was surprised to find out her attacker is out of prison four years early. She said earning two bachelor's and an associate's degree behind bars does not prove rehabilitation.

"You can get educated but does that mean you're changed as a person, does that mean he's not going to rape somebody else?" asked Wheatley.

Supporters of Indiana's prison education program argue an inmate earning a degree or learning a trade is less likely to end up back in prison. Critics contend an inmate's education should be reward enough and say inmates are just completing degrees to get out early.

"Isn't that enough incentive for them to provide themselves with a future, then we have to continue to go on top of that and say, 'Oh and we'll let you out of jail early too, and offend these poor victims,'" said Elkhart County (search) district attorney Curtis Hill.

The education is mostly taxpayer funded, but prison officials say it's still cheaper than keeping an inmate in prison. And inmates say it will be better for society in the long run.

"This money is being used to enhance our condition so when we do re-enter society we could be more productive," said inmate Kenneth Brewer.

Indiana lawmakers are under some pressure to change the rules and are looking at capping the amount of time inmates can learn-off of their prison terms.

Click in the box near the top of the story to watch a report by FOX News' Steve Brown.