Oscar Robertson’s high school team in Indianapolis was the first all-black basketball team in the nation to win a state title. What should have been a joyous culmination to that 1955 season became a seminal moment in the life of a young man who would become an NBA legend.

Tradition had the winning team climbing aboard a fire engine and being lauded downtown in Monument Circle. That was the route taken when Milan High, the team that inspired the 1986 film “Hoosiers,’’ won the title in 1954.

But not this time, not with this team, which was quickly shuttled past the Circle. “Since we were black,’’ Robertson said recently from Cincinnati, “they decided we were going to tear up the town and they took us to an all-black community center.’’

When his team won its second state title the following season, Robertson went home.

The first championship team was celebrated 60 years later in the Circle, but the original stain was a conscience-raising experience that Robertson, who became known as “The Big O,’’ has never gotten over.

“When you’re young, you don’t forget,’’ said Robertson, 78. “People tell you what you can do and can’t do, it’s almost like animals in the forest. From the time of birth, what you can do and what you can’t do here in America. I knew I couldn’t ride in the front of the bus. I couldn’t go in a family restaurant. I couldn’t go to a lot of places. I’ll never forget when Floyd Patterson fought Ingemar Johansson in Indianapolis. Patterson couldn’t even go into some of the restaurants.’’

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Robertson embraces black athletes who speak out, but he said the statements are more impactful when they come from successful players. He lauded LeBron James for countering when Knicks president Phil Jackson used the racially tinged term “posse’’ in describing James’ business associates.

“LeBron earned the right to speak out through his play,’’ Robertson said. “When you win and you’re a star and there’s no doubt about it, people expect you to say certain things. And I’m glad that he is saying things that are right.

“It’s really amazing that some whites, maybe they don’t like LeBron’s stature in this position. They always want to come back and say something about it. LeBron took some of his school friends and made them into millionaires. Maybe that’s what they didn’t like about it. It’s sad to say, but when you start to make money as a black person, people don’t like you.’’

OPPONENT ALSO REMEMBERS SLURS

Robertson was first noticed at Crispus Attucks High School. Bobby Plump, the Milan High point guard characterized in “Hoosiers,” played against Robertson’s team in a state tournament game in 1954. “I had 28 in that game, he had 22,’’ Plump said from Indianapolis. “Normally, I don’t tell people that — he was only a sophomore.’’

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Plump, 80, said he heard racial slurs from motorists in downtown Indianapolis before Milan’s game against Robertson’s team. “People would stop, roll down their windows and yell, ‘Beat those [expletive]!’ ’’ Plump said. “It shocked the hell out of us. There was prejudice, absolutely. We said, ‘What are these people talking about? What’s the matter with them?’ ”

Plump followed Robertson’s progress through college at Cincinnati and then to the NBA, where the 6-5 guard became a 12-time All-Star en route to the Hall of Fame. In the 1961-62 season, his second in the league with the Cincinnati Royals, Robertson became the only player in NBA history to average a triple-double for the season with 30.8 points, 12.5 rebounds and 11.4 assists. He holds the NBA record with 184 triple-doubles in a 14-year career. But Robertson’s triple-double average went largely unnoticed when it occurred.

“We had no idea of what was going on,’’ former Royals teammate Bucky Bockhorn said from Dayton, Ohio. “We’d go out for a beer and look at the stat sheet and he’d have 27 points, 12 rebounds, 14 assists, and you just took that for granted. It was rarely spoken of.’’

Thunder guard Russell Westbrook (31.0 points, 10.4 rebounds, 10.3 assists) is trying to become only the second player to average a triple-double, and it’s all the current rage around the league.

Charley Wolf, 90, was coaching the Royals when Robertson accomplished the feat. “Remember that years ago you had to battle Bill Russell, [Wilt] Chamberlain, [Clyde] Lovellette inside,’’ Wolf said from Cincinnati. “They were much bigger.’’

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Robertson averaged 30.3 points, 10.4 rebounds and 10.6 assists per game in his first five seasons. In addition to the triple-double season, he had four other seasons in that span in which he averaged at least 28.3 points, 9.0 rebounds and 9.0 assists per game.

Robertson said Westbrook’s run at his record is “great for the public,’’ but that in his time, “they probably missed tons and tons of assists with players. Now, everything is an assist. If I throw the ball and you dribble it eight or nine times and get a long shot, it’s an assist.’’

FREE AGENTS OWE THANKS

One of Robertson’s biggest contributions to the NBA also is largely unnoticed. He was the president of the National Basketball Players Association from 1965-74 and in 1970 led a class-action lawsuit against the league to end the reserve clause, which bound a player to one team for his entire career. It became known as the Oscar Robertson Rule and eventually led to free agency and today’s huge salaries.

“I’m not sure that today’s players will equate Oscar Robertson with the largesse they’ve encountered with free agents. They think of him more as a triple-double guy,’’ said Len Elmore, who played in the NBA from 1974-84 and now is an attorney and ESPN sportscaster. “They think of him as a great player, but I’m not so sure that most of these young people will understand the lengths to which he went to try to create an atmosphere of free agency and give players that ability to move from team to team. Nobody talks about this rule even though they talk about how much money the guys are making. To appreciate what you have, to know what those who preceded you went through in order to attain the rights and abilities you have now. I think you can broaden that to the whole civil rights experience.’’

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Robertson never made more than $250,000 a season. Today’s minimum salary in the NBA is close to $875,000. As Westbrook chases Robertson’s triple-double average, his 2016-17 salary is a reported $26.54 million.

“I’m happy that the guys are making the money,’’ Robertson said. “Before the Oscar Robertson case, for so many years, players were restricted. I’m glad that LeBron is making millions and millions of dollars so his family will never have to worry about money again. I played when I played. I played against some of the greatest players in the history of basketball who are in the Hall of Fame, and no one can take that away from me.”