To understand how he does what he does, every day, you have to take a step back, way back, to a grandmother who told him these words: "The more you know, the more you owe."
"I didn't understand at all, she said to me, 'Junior, you'll understand when you grow up,'" said Dr. Marshall. "I wouldn't be the person I am today without my grandmother, there's no doubt about it, and I wouldn't be doing what I'm doing without her."
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He lived by those words, but as he became an adult, and then a teacher in San Francisco while the crack epidemic raged, he found it wasn't working. He'd expect brilliant students to go onto college after his class. Instead, he spotted one in the Tenderloin.
"He said, 'Mr. Marshall, Mr. Marshall! You're the best teacher I ever had, I only went to school for two classes, PE and your math class, you were great!' But he was strung out on drugs," said Dr. Marshall.
He would get letters, thinking they were from college dorms, only to find they were from prison dormitories. Worst of all, he began attending funerals of his former students.
"I mean, I was devastated," said Dr. Marshall. "I began to realize that them being with me 55 minutes a day, 180 days a year, wasn't producing the results that I wanted."
In 1977, he co-founded the Omega Boys Club, sending out postcards and inviting former students. He said the group would be a violence-free, drug-free academic-oriented organization, saying to the members: "'Tell me everything you didn't tell me in math class, tell me what's going on in your home, tell me what's going on in your neighborhoods."
He says he wanted the backstory, "Together we would figure out how they would navigate all of that so they wouldn't end up dead, incarcerated or on drugs."
And not knowing how, he made them a big promise, or as he prefers to call it, a "commitment." If they worked hard, he'd find a way to send them to college.
"I didn't have a dime! You have to be a little crazy if you don't have any money," said Dr. Marshall.
A year later, the first eight students were ready for college and it was time to make good on his word. He says that's when the first miracle happened.
"I always tell people if you don't believe in miracles, I'm the wrong guy to talk to because I believe in miracles," said Dr. Marshall. "A reporter at Channel 7, his name was Steve Davis, came out to the club."
We found the archival footage, and it is a sight to behold. Davis did a series on the Omega Boys Club. Inspired by his reporting and the club's story, ABC7 News viewers started sending in donations. Davis got to present the club with a life-changing envelope.
In Davis' words: "Several hundreds of viewers, bless you, have sent cash and checks to the Omega Boys Club. I asked the Omega Boys why they think people from all over the Bay Area are sending them money." In this moment preserved on film, filled with joy, a young man beams at the camera, "Why? Because they care for us."
Now, Dr. Marshall has helped 226 students attain their college degrees and their photos line the walls of his classroom, both young men and women smile out from these graduation portraits. To date, he's helped raise funds and give out more than $7 million in scholarships. He remembers every one.
People like Shamann Walton, who we caught up with last year when he was president of the San Francisco Board of Education. When he joined the club in 1993, he had spent time in juvenile hall and had been expelled multiple times.
"I may not be a free man today and I may not be alive without the mentorship and the knowledge that we received from the club," said Walton.
We spoke with two other graduates who say they were impacted by Dr. Marshall -- Sakari Lyons from the Bayview and Mike Gibson from East Oakland. Both had mothers addicted to drugs and both entered the foster care system.
"I'm just like the train that just can't stop," said Lyons. "I told him, 'Dr. Marshall, I'm going to make you proud, I'm going to make you real proud."
Gibson was an eighth grade dropout, and was serving time by 16.
"When I met Dr. Marshall, he saw something in me that I didn't see in myself," he said.
And this is where you see the ripples of Dr. Marshall's work.
Walton is now running for city supervisor.
Sakari Lyons is a professor, has a family of her own, and works with a program that helps African-American women develop life skills and have healthy families.
Gibson went on to earn a Masters, is a father, and is now the executive director of the Alameda County EMS Corps, which helps prepare young men of color become EMTs, firefighters and paramedics. He's helped 176 graduate from that program.
Dr. Marshall's life philosophy has become theirs, too.
"The more you know, the more you owe," said Lyons.
Dr. Marshall's grandmother likely couldn't have guessed how far her message would spread.
"I've been on Oprah twice and Oprah used that phrase!" said Dr. Marshall. "I said, you can say whatever you want as long as you say: Dr. Marshall's grandmother said 'the more you know, the more you owe.'"
He's gotten to meet many of his icons, presented with awards by Denzel Washington and even seated next to Rosa Parks. But for Dr. Marshall, it always came back to making one woman proud. He still thinks about his grandmother every day.
"This may sound crazy, but I actually talk to her," said Dr. Marshall.
She hasn't answered back yet, but he says he can imagine what she'd say.
"She would say I was doing the Lord's work, which really made me feel good and still does," said Dr. Marshall.
The Omega Boys Club is now called Alive & Free. At 70 years old, Dr. Marshall still teaches his classes every week. He says changing lives is easy, it's the fundraising that is the hardest. If you'd like to donate to his cause, visit Alive & Free.
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