The N2 highway at Grabouw was re-opened on Monday after protesters disrupted the flow of traffic in the morning, Western Cape police said.
"At this stage, it is quiet although tense. Police are on the scene and the N2 has been opened," Captain Frederick van Wyk said.
He said a group of people threw stones in the morning and barricaded the road.
An SABC crew was pelted with stones while broadcasting from the scene for the morning radio news.
Stun grenades and rubber bullets were used to disperse the crowd.
Van Wyk said the unrest was apparently about service delivery grievances related to education.
"Nearly 2000 people are marching to the Groenberg high school," he said.
"The Slangpark informal settlement borders the N2 highway and people from this community and the nearby Chotzoben informal settlement, on the Old Cape Road, are protesting."
The provincial education department said the protesters were members of the Elgin Grabouw Civic Organisation, who had planned to march in Grabouw on Monday to hand over a memorandum of demands to education MEC Donald Grant.
Organisation chairman John Michels was quoted in the Cape Times as saying: "If he is not here to receive it, we will march to Cape Town."
The troubled Umyezo Wama Apile combined school in Grabouw was closed last week until April because of teaching disruptions.
Civic organisation members barged into the school two weeks ago to demand that a new school be built.
Some facilities were set alight and a number of people were arrested for public violence.
Last week, classrooms were stormed by members who demanded that teaching stop.
They told pupils that Grant had not responded to a memorandum in which the group demanded that new classrooms be built.
Grant said he responded to the memorandum and was doing everything he could to obtain a site for a new school.
According to his spokeswoman Bronagh Casey, he would brief reporters later on Monday on the ongoing protest action, giving a timeline of events and a plan going forward.
