Johannesburg — Asked what he will do now that he has graduated from high school, a black student from Soweto says confidently, ''I will go to work.''
Three friends gaze at him with some amazement. One wags his head. ''Haven't you seen today's newspaper about how many people are being retrenched?'' he said. ''You won't find a job.''
The friend may be right. Unemployment is rising dramatically in South Africa, hitting hardest at blacks. Economists here are warning of a jobs crisis unmatched in the postwar period.
At first glance, statistics on unemployment among South African blacks - 7 percent, according to the government - do not look serious. But analysts say this number is qualified in such a way as to be practically meaningless in terms of reflecting total unemployment in South Africa. Other estimates from academicians put the unemployment rate at about 24 percent - mostly made up of blacks.
''These are not happy figures,'' leading South African businessman Harry Oppenheimer said recently in reference to rising unemployment. He warned starkly of a ''real risk of industrial disturbances and political instability.''
Rising unemployment comes on the back of an already high inflation rate of 14 percent. Together these factors are producing severe economic hardships for blacks. Deprived of political rights, blacks have taken to the streets in a few instances to vent their frustrations over bread and butter issues.
Most recently, black townships near Durban have been the scenes of unrest over a 12 percent increase in bus tariffs. Buses were stoned in a general mood of dissatisfaction - not only over fare hikes, but also over recent food and rent increases, says a spokesman for Soweto blacks.
The immediate causes for South Africa's economic decline are the lower price of gold, which is the country's biggest export earner, and belated effects of economic slowdown hitting all major Western economies.
However, more basic to South Africa's economic decline is its apartheid policy, many economic analysts say. In pursuing its policy of strict separation of the races, the government has greatly distorted the economy. The government's massive control over industry and labor has worked mainly to the detriment of blacks, analysts say.
Mr. Oppenheimer, who retires as chairman of Anglo American Corporation this year, said recently that the newest example of the government's forcing the economy to support apartheid is the proposed southern African development bank. The bank's aim is to encourage a dispersal of industry closer to the black ''homelands'' that were created to remove unwanted blacks politically and physically from ''white'' areas.
Mr. Oppenheimer questions the wisdom of deflecting growth from the major metropolitan areas. ''What imperative is there to stop or even slow down significantly development in these areas - particularly in a time of recession?'' he wonders.
Apartheid also bites harder during recession in another way: The government has stepped up control over blacks living in ''white'' urban areas, acting more harshly against ''illegals'' to discourage blacks from flocking to the cities for badly needed jobs.
A young black man from Soweto says there is a noticeable increase in the number of young people out of work. ''A person my age used to not dare line up for unemployment insurance'' because it was seen as something only older workers should need to rely on, he says. ''Now it's socially acceptable.''
To survive in this downturn, blacks have grown more reliant on informal credit systems. In most neighborhoods in Soweto, for example, families contribute voluntarily to a pool that families can eventually draw on. Other informal arrangements have the effect of community saving that can be used to help the unemployed during a time of need.
Although the government is not about to dismantle apartheid to ease the economic problems facing South Africa, it does regard the present downturn seriously. Simon Brand, chairman of the government's economic advisory council, says inflation is the main worry over the next year.
While conceding that social risks of rising black unemployment are ''serious, '' he says they fall within ''bounds that can be handled'' as long as the job situation begins to improve a year from now. Should the economy fail to begin growing late in 1983, he says, unemployment could take over as the top concern.
But some forecasters have estimated the nation needs at least 5 percent real growth annually just to keep up with the expanding, mostly black labor force.