The children were packed into two school buses and wore similar pastel clothing. But as they emerged, it became clear that one bus held mostly black children, the other one whites.
A video of the excursion to a safari camp from a private school in Pretoria went viral in South Africa on Thursday, tapping into an enduring and difficult national conversation about race. Teachers were shown leading the white children in one direction and the second group, almost exclusively black, in another direction.
It was the second time in a year that the school, Curro Foundation School Roodeplaat, faced accusations of racism.
More than two decades after black majority rule spelled an end to apartheid, South Africa faces regular, troubling incidents of racism, the majority on social media, but many involving physical violence and taunting.
The Curro Foundation School Roodeplaat video, uploaded on YouTube, was blurry, but the racial separation was clear. A statement from the school said the two groups had been divided on the basis of language, not race. Earlier this year, when it was accused of segregating classes based on race, the school argued that pupils were distributed according to friendship groups.
The Curro group runs 42 schools throughout South Africa, most of them taught in English.
The school statement said Curro Foundation School Roodeplaat offered students the choice of being taught in English or Afrikaans, a language largely spoken by whites. It said the vast majority of whites preferred an Afrikaans-speaking environment and the majority of black pupils preferred English. It said two-thirds of the students at Curro schools around the country were black.
"Thus, in a classroom in which the language of instruction is Afrikaans, the overwhelming majority will be white students. In a classroom in which English is the language of instruction, the vast majority will be black learners," the statement said.
"So when a school outing occurs, what you see in the classroom is what you will see on the outing. Not a division based on race -- but a division legitimately based on the language preference of the class," the statement said.
But South African Twitter users Thursday erupted with outrage as a hashtag #CurroMustFall sprang up.
"This #Curro situation is completely unacceptable. Lame 'divided by language' excuses don't fly. You do not divide us by our race," tweeted a radio host, Rob Forbes.
Last month, the Gauteng provincial education department ordered a review of the school's operating license after an investigation found that its segregation of classes at the beginning of the year was racist. The investigation was ordered after parents signed a petition demanding to know why some classes were white-only and others were black-only.
Gauteng Education Minister Panyaza Lesufi expressed disgust Thursday at the school's explanation that the children were divided in language groups, and threatened to revoke the school's license.
Referring to tribal languages, he said: "The day we allow Tswanas to only play with Tswanas and Xhosas only play with Xhosas, that will be a sad day for this country .... These are 6-year-olds. They can play together."
Lusufi said he would decide what to do about the school after he receives the results of an investigation. He said the decision "is not going to be nice, that I can assure you."