The supporters in blue Democratic Alliance regalia braved the scorching sun, using placards to shield themselves.
DA Parliamentary leader Mmusi Maimane is scheduled to address the crowd.
Some of placards at the event read: “Free higher education” and “1 million internships”.
Many of the people in the crowd were wearing different school uniforms.
Monday marks South Africa’s 38th anniversary of the 1976 Soweto uprisings.
On 16 June 1976, a group of schoolchildren set off from Morris Isaacson High School in Orlando, Soweto, to protest over Afrikaans being the medium of instruction, among other grievances against the apartheid government.
There was a stand-off with police, who opened fire on the children. The township was sealed off and attacks on government buildings followed, as well as the flight of many youths and political leaders into exile.
This day is now celebrated as youth day.