Inside, Carroll works with a population of men who are desperate to change. Her mission: to help them do it.
"A lot of these people can't even look at themselves in the mirror," Carroll said. "They're just afraid because they've got so much baggage behind them."
Carroll first started working with San Quentin inmates in 1994, as part of her late husband's ministry. She helped start a self-help group in the prison in 2000.
But over the years, she saw a greater need for a more intensive pre- and post-release program.
"I saw a young man struggling to put together his parole plans ... from inside the institution," said Carroll, who started her nonprofit, the California Reentry Institute
, in 2009. "Seeing someone denied parole because they didn't have solid plans, I decided there had to be more."
Today, Carroll's program targets emotional and social change and teaches life skills to help inmates successfully transfer from prison to society.
"What I do doesn't give a lot of people the warm fuzzies," Carroll said. "The reality is, any life is worth helping."
The program is voluntary, requires a minimum 24-month commitment and has a strict attendance policy. It requires that students take responsibility for their actions. They work to understand why they committed a crime and how to change to be a productive member of society.
"We spend an entire year alone on emotions so (they) learn the causative factors of what got them where they got in the first place," Carroll said.
Carroll also opened a transitional house to provide a safe and supportive environment for men who complete her program inside San Quentin.
She offers job training, case management and other services to ensure the men stay on the straight and narrow.
"These men are hungry. They really want what we have to offer because ... they want to be better people," she said.
CNN spoke to Carroll about her work. Below is an edited version of the conversation.
CNN: You've developed a really intensive program. How does it work?
Collette Carroll: The men meet every Saturday either for class or individual case management. They have to do an accountability statement, and that is 100% being accountable for the harm that you have caused to your victim, your victim's family, your family, society at large.
And then we follow them, should they choose, when they get out. We try to demystify everything so that when they do step out, they feel empowered to succeed.
We have been lucky enough so far to have graduated one class after 27 months. And we are close to completing our second program. The current class has 50 participants, and I continue to work with 14 of the graduates from our first class.
We have a zero percent recidivism rate for the men who continue to be part of our post-release program and are doing well, giving back and are contributing members of society.
CNN: What's your overall approach with your participants?
Carroll: We call them clients because that's the way we see them. We're there to come alongside them, to help them see where they were, where they are, how to get where they need to go, to help them understand that they have an option. That they can actually have a dream. And when they get in touch with their feelings, then they understand.
It's our obligation, I think, to keep society safe. We have to teach them the skills to be successful people when they re-enter society. So we start with, "Can change happen?" We go through abandonment. We go through guilt and shame. We get into relationships. That's what this is about, unpacking the baggage.
CNN: Successful re-entry is a huge part of what you do. How does your post-release program work?
Carroll: When we meet them, they get fresh linens, clothes, shoes. They are provided with a prepaid 30-day cell phone so they can contact their family, their accountability partners and their sponsors. They have rules and regulations they have to follow. Number one: the parole rules -- 100%, no varying.
We help them reintegrate into society, going on BART (rapid transit), riding a bicycle, cooking. Just all the things that are everyday life.
CNN: What's your secret to success?
Carroll: Our success rate, I think, stems from the men who are doing the really hard work and the fact that they feel that if they get in a difficult situation, they can reach out for help and have someone see them through the tough times.
Our program is not easy. It's an intense curriculum. We expect a lot from them. They're the ones that make the change. All I can do is give them the tools to do it.
Want to get involved? Check out the California Reentry Institute website at
www.californiareentryinstitute.org and see how to help.