Sochi, Russia

In the 150 years since soccer was invented on the muddy playing fields of English boarding schools, the sport has changed so much that it would be almost unrecognizable to the blue-blooded boys who kicked around a heavy leather ball.

But it hasn’t changed completely.

Because in a small outpost on the Volga River, a gray-haired 71-year-old who walks with a cane, the man they call Maestro, is still educating young men to carry themselves with character—and win World Cup games.

His name is Óscar Tabárez. And in 12 years in charge of Uruguay’s national team, he has helped turn a country of 3.5 million into the best pound-for-pound team in world soccer by treating his players as if he were a housemaster at Eton or Harrow.

Just as any British boarding school, Tabárez has long said his primary goal was to mold well-rounded men. He imparts lessons about respect, decency, and the importance of good manners. At Tabárez’s request, Uruguay might be the only team in Russia to have its squad of millionaires share bedrooms for the duration of the tournament. And they drink tea constantly.

“He would always say that being a football player is a profession but it is the way you behave as a human being that is important,” said Diego Forlán, a former Uruguay captain under Tabárez. “You can be a talented player, but if you don’t behave well, it’s going to reflect badly on you and your teams.”

Nothing reflected worse on the team than its record in the years before Tabárez took over in 2006. Though Uruguay won World Cups in 1930 and 1950, when squads were still traveling to the tournament by boat, the modern era had been less kind to them. The team hadn’t been near a World Cup semifinal since 1970. And it missed the 2006 tournament entirely. Worse still, Uruguay had earned a reputation as playground bullies with their reckless and physical play.

Uruguay manager Óscar Tabárez, right, shouts out during a match against Russia. Photo: Gregorio Borgia/Associated Press

When Tabárez was called in to fix it, he immediately identified the problem. Uruguay had talented players, but lacked the structure to turn them into upstanding citizens. He drew up a plan to revamp the training of the national teams, a dossier known by the catchy title, “Project for Institutionalizing the Processes of the National Teams and the Training of Their Soccer Players.”

The document wasn’t so much a tactical or technical treatise as a charter for his program. “A young talent should train and prepare for life’s challenges,” Tabárez wrote. “The young person must study, we shouldn’t obstruct that, we should favor it, it increases their sporting potential.”

Other managers at the World Cup simply coach the senior squad. But Tabárez became the dean of the entire men’s national program, from the Under-15s to the team that travels to the World Cup. Every member of those squads would come to train under Tabárez at the national training center, where he could shape their development as players and as people.

First, the setting had to be right. The Celeste Complex outside Montevideo needed to foster a sense of heritage—and, unlike Eton, Tabárez didn’t have a long line of British prime ministers to point to. So he started by commissioning a giant Uruguayan crest for the lobby. He decorated the walls with black-and-white photos of players who had fought for the team’s colors before. And outside, he ordered the federation to install a fogón, a traditional Uruguayan grill that doubled as a campfire, where he could sit with the players and tell stories at night.

Tabárez’s professorial air is no coincidence. Before he went into management full time, he was an elementary-school teacher. To this day, he likes to educate his players on history, geography, the arts, and anything else he happens to find interesting in the moment. This too is part of the Tabárez curriculum.

“One time we played in Japan and we were talking about how we were surprised by the culture,” said Forlán, an analyst for Telemundo Deportes at the World Cup. “So after dinner, the Maestro got the lads together and we listened to him talk about Japan, its history, everything that has happened in the country. He is a very knowledgeable man.”

Uruguay's supporters dressed as students as they paid tribute to Uruguay's manager Óscar Tabárez. Photo: Lavandeira/Zuma Press

Tabárez organizes trips for young players to attend museums and the theater. He engages his players on subjects as diverse as classical music and botany. “What Tabárez knows about plants is tremendous,” Claudio Pagani, who runs Uruguay’s national training complex, has said.

Tabárez is also a stickler for good manners. Many a Uruguayan star has run afoul of his no-muddy shoes rule. And there are strict rules about not leaving plates on the table or putting feet up on chairs. The use of cellphones is prohibited at breakfast, lunch, and during team talks or meetings.

Tabárez wants the players to talk to each other, even if it’s only hello.

“When the kids arrive from the U-15, we say that here are two things that can’t be missed: The way you greet people when you arrive and how you interact with the people who work here,” he said in a new book, “Maestro: The Legacy of Tabárez” by Luis Eduardo Inzaurralde and Jorce Señorans. “It doesn’t matter if you don’t know them, it is a sign of coexistence and respect.”

That also extends to the field. Before Uruguay competes in any tournament at senior or youth level, Tabárez lectures the team on what behavior is expected of them. His message is always the same: No fouls, no bad conduct, and whatever happens, no back talk to the referees.

Like every teacher, the Maestro knows that some lessons go in one ear and out the other. During his time in charge, he has overseen striker Luis Suárez commit a deliberate handball in the 2010 World Cup finals and bite an opponent at the 2014 World Cup, for which he was suspended from all soccer for four months. His team has also racked up eight red cards at tournaments, plus countless yellows, including a whopping 18 in six games at the 2011 Copa America, since he took over in 2006.

Uruguay's Luis Suarez shoots at goal from a free kick. Photo: max rossi/Reuters

Still, Uruguay captain Diego Godin said Tabárez continues to tell players how disappointed he is with them, even when they are sent off while playing for their clubs. And Suárez credits the Maestro’s exhortations with turning him into a reformed character.

No matter what happens to this team at this World Cup, Tabárez’s mission to educate Uruguayan players on matters away from the field will continue. He is considering making English lessons available for all youth-team members and providing them with counseling that covers basic contract law to help them navigate the world of professional soccer.

Above all, he wants to keep them in Uruguay for as long as possible, where they can graduate from the Maestro’s school for upstanding soccer players.

“It is as I say to the players of the National Team,” Tabárez said. “You can make good contracts in clubs, gain prestige, but there are some things you can only get playing for Uruguay.”

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Write to Jonathan Clegg at jonathan.clegg@wsj.com and Joshua Robinson at joshua.robinson@wsj.com