WALTHAM -- All these years later, he still seethes at the indignity of it all: the color-coded shirts (white for newbies, black for kids slogging through their penance, orange for kids hoping to get sprung), the beatings with a paddle for transgressions as mundane as a sidelong glance, the way, when he got out, his neighbors looked right through him as if he didn't exist.

"Yo, whatʼs up?" 11-year-old Marcus Smart said hopefully when he returned from the Alternative Education Program (AEP) to be with his homeboys again.

They didn't crush him with slurs or insults. They slayed him with silence instead.

"Nobody would talk to me," Smart said. "I was the bad kid."

He landed in the AEP after being thrown out of his elementary school for bashing his classmateʼs head on the sidewalk.

He doesn't ever want to be that kid again. He is consumed with changing the narrative so people will stop passing judgment and appreciate how far heʼs come. He wants Boston to embrace his intensity, not question it.

The gravity of his basketball journey has been staggering. He is not just playing for himself but for his family, which has been pocked by tragedy, a responsibility he terms "an opportunity God has provided me."

Danny Ainge is betting that Smart's on-court intensity will be a good fit in Boston. Brian Babineau/NBA/Getty Images

His mom, Camellia Smart, trudges to dialysis three days a week and was bounced from the waiting list for a kidney transplant because she couldn't guarantee sheʼd be around on a momentʼs notice, not when she needed to be in Stillwater, Oklahoma, to watch her son.

His father, Billy Frank Smart, is also experiencing health issues. Michael Smart, his brother, was once a promising basketball prospect who crippled his chances by choosing drugs and gangs instead. Another brother, Jeff Westbrook, experienced his share of squandered opportunities and pleads with Marcus not to make the mistakes he made.

"Marcus is playing for all of us," said Michael Smart. "Sometimes it can be a lot."

Yet itʼs the legacy of his late brother Todd Westbrook, gone from cancer at age 33, that weighs most heavily. Todd was 15 years old and coming off an all-district basketball season in Lancaster, Texas, when they discovered a tumor behind his eye.

One night, in the wake of the needles and the chemotherapy and the radiation, Todd checked himself out of the hospital, his left eye swollen shut, and scored 30 points. He was dubbed the Comeback Kid, but over time the cancer sapped his strength and stole his dreams.

Near the end of Toddʼs life, Marcus perched himself at the end of his brotherʼs bed and fed him rolled-up socks to shoot at the wastebasket, the only thing Todd could hoist in the advanced stages of his disease.

When he died, his surviving brothers corralled a sobbing Smart and sat him down.

"Iʼll never forget it," Smart said. "They told me, 'Todd is gone, Mom is sick, Dad is sick, and you are all we've got.' My older brother Jeff told me, 'I had my chance, Mikey had his chance, and we blew it. Now itʼs your chance. Weʼre depending on you.'"

Marcus nodded, but he was only 10 years old. He was too young to understand, a little boy who was angry his brother was taken from him.

Well-meaning family friends tried to console him by reminding him he was tough, just like his mom, just like Todd, but the toughness Marcus embraced was misguided.

He broke windows and pelted rocks at strangers. Marcus had good aim; he nailed a guy on a bike, only it was a gang member who left Smart running for his life, bullets whizzing past his ear.

The violence, the drugs and the gangs were a regular feature of his South Dallas landscape, a gritty canvas that corrupted his brother Michael, who nearly died from a cocaine overdose.

"I could have ended up just like Mikey," Marcus said. "I was all around it. Saw my friends sell drugs, saw them buy them from my brother.

"There was a crazy path I could have taken, but even though my brother was wrapped up in it, he did everything he could to keep me away from it."

Mikey told Marcus to always stand up for himself, so when a classmate hurled objects at him out the school bus window, he confronted him.