South Africa is marking 30 years since the Soweto uprising, a student protest pivotal to the apartheid struggle.
The image of Hector Peterson became symbolic of the struggle
President Thabo Mbeki led a march along the route taken on 16 June 1976 by black students fighting a policy forcing them to learn in Afrikaans.
Relatives of the children killed when police opened fire cried as wreaths were laid in their memory.
The BBC's Peter Biles says the events celebrate the role played by young people in the fight against apartheid.
But our correspondent says they are also a reminder of their sacrifice and of the challenges which lie ahead for young South Africans today.
The Soweto uprising and the riots that spread to other township are seen as a milestone in the growth of the movement against white minority rule, which was finally ended in 1994.
In a sombre speech, Mr Mbeki told a crowd of some 20,000 people at the FNB stadium that young South Africans were confronted by poverty, unemployment, alcohol and drug abuse and Aids.
He accepted that a lot still had to be done to improve the education system.
The commemorations began at the Morris Isaacson High School where the first march began 30 years ago, before proceeding to the Hector Peterson memorial, named after the first and youngest student to die in the protests.
He was caught on camera as he died in the arms of a fellow student, in a photograph that became iconic in the struggle against white minority rule in South Africa.
Poverty remains a big problem in Soweto
His mother Dorothy Molefi and President Mbeki were among those to lay wreaths at the memorial, watched by hundreds of people who observed a minute's silence and then sang the Zulu struggle song "Senzeni na?" ("What have we done?").
"I remember that day - it was like death to me," Isabel Boto, 70, told the BBC News website, recalling 1976.
"I am here to honour the children. I am very happy now, I never thought this day would happen."
Jeremiah Nkotsi, 21, said the day meant a lot to young people too.
"It brings the memory of those who died to let us be free, to let us be what we are today."
BBC Africa correspondent Orla Guerin says there is now a feeling that Soweto is starting to turn the corner and move away from being seen as a deprived township on the outskirts of Johannesburg.
The area's first two shopping centres have been built in recent years and a four-star hotel is to be opened in October.
President Mbeki said South African youth still faced many hurdles
But in some parts, the old problems of poverty, unemployment and crime still remain.
Archbishop Desmond Tutu told the BBC's World Today programme that South Africa's continuing poverty was a "powder keg".
"Unless we do something about that quickly, we may find all our achievements are a puff of smoke," he said.
In Soweto, red paving stones symbolising spilled blood have been laid along the route the protesters took in 1976 from Morris Isaacson High School to the Orlando West neighbourhood where the fateful confrontation with police took place.
The government said that 95 black people had been killed, but unofficial estimates put the number of dead closer to 500.
At the time, Winnie Mandela, the wife of then-imprisoned ANC leader Nelson Mandela, described the protests as "just the beginning".
Domestic and international pressure eventually led to the release of Mr Mandela in 1990 and the country's first non-racial elections four years later.
Mr Mandela was overwhelmingly elected to become South Africa's first black president.