Johannesburg — The South African government is attempting to squelch and preempt black protest in an apparent bid to avoid further embarrassment to its avowedly ''reformist'' new Constitution.
But the effort is having mixed success. There continue to be isolated clashes between blacks and police in townships and schools south of Johannesburg. Thirty-one people died in such clashes last week.
The government's steps to cut off protest include:
* Circumventing a significant court ruling that resulted in the release late last week of seven security prisoners.
The government quickly ordered the rearrest of the seven and issued new detention orders for others held since elections last month for new Indian and Colored members of Parliament.
The court said the government had not given reasons for the detentions. But the government responded by saying in its new detention orders that such information was not in the public interest.
Eighteen people were arrested under South Africa's security laws last month in connection with the elections. Most of them are affiliated with the United Democratic Front, an organization that urged Coloreds (people of mixed race) and Indians to boycott the elections.
* Starting school holidays for blacks a week early in a number of townships near Johannesburg.
Many students have been boycotting classes. Analysts see the government's move as an attempt to end black students' use of the schools as a platform for protest.
* Slapping a blanket ban on public meetings scheduled for last weekend in the Johannesburg area. Meetings affected were those connected with recent unrest and those planned to commemorate the death in detention of Black Consciousness leader Steve Biko, who died in police detention on Sept. 12, 1977.
A ban on all gatherings in the troubled townships south of Johannesburg has been imposed until today.
A spokesman for the Detainees' Parents Support Committee, which monitors security arrests, says, ''The intensity of security force activity right now is very high. It relates to the amount of political resistance'' to the new Constitution and economic and educational issues, he asserts.
The parents support committee says that so far this year more people have been held by the security police than in all of 1983. The group says there have been 572 detentions without trial so far this year.
The latest addition to the numbers appears to be Saths Cooper, deputy president of the Azanian People's Organization. AZAPO is a Black Consciousness organization that urged Coloreds and Indians to boycott the elections last month. Mr. Cooper was apparently arrested on Sunday.
The government's ban on gatherings did not stop blacks from staging funeral processions over the weekend. The funerals were for six young blacks killed in unrest that preceded the last week's upheaval. The police say investigations into those six deaths, which did not take place in the townships hit last week, have shown police were not responsible.
A black man was killed over the weekend in Katlehong, a township near Johannesburg. He was apparently shot by police after blacks attacked the home of the mayor of the township and burned it to the ground.
The cause of last week's upheaval in five townships south of Johannesburg was an increase in rents, many analysts say. Residents of the townships and the mayor of the black town council, Esau Mahlatsi have met.
The mayor has said the rent increase will still be implemented. But he has promised financial assistance to families that cannot afford the increase.
Last week South African Minister of Law and Order Louis le Grange said he was convinced the rent increase was not the reason for the unrest.
''There are individuals and other forces very clearly behind what is happening,'' he said, refusing to elaborate.
Bishop Desmond Tutu, Dr. Alan Boesak, and other church officials have met with government ministers responsible for black education and black affairs in general. Tutu dismissed the claim that ''instigators'' were primarily responsible for black unrest.
''It is playing games and is unrealistic to talk about instigators when the grievances are real,'' he said.
Meanwhile, South Africa's new tricameral Parliament is conducting business in advance of its formal opening later this month.