A top-level study of education in South Africa undertaken at the government's request has criticized the education offered blacks and urged "freedom of choice" for students and parents so schools can decide for themselves whether to admit pupils of all races.

The year-long investigation, by the Human Sciences Research Council, the country's main think tank, is extremely sensitive politically for the government because it raises questions about the feasibility and practicality of having four completely separate education systems for the country's four main racial groups.

The council's report proposes one national education ministry to oversee regional education authorities that would operate schools.

A segregated school system is one of the basic policies of the ruling National Party, which is now contending with a right-wing trend among white supporters who would view even minor alterations in that system as a move to "sell out" whites.

The government's initial response to the report released here today was to thank its mainly white drafters, state that it has "reservations" about parts of it and reaffirm the policy of segregated schools.

The government asked the council to do the study to meet criticism from the country's black, Indian and Colored (mixed-race) populations about their education and to respond to serious discontent among white teachers about working conditions.

White Education Minister Gerrit Viljoen neither accepted nor rejected the proposal for a ministry whose main purpose would be gradually to achieve parity in educational financing for all students regardless of race. The government will make a more detailed response next year, he said.

Countering political pressures from the right however, is the government's self-interested awareness of the need to improve education for blacks, who outnumber whites five to one, in order to alleviate the glaring shortage of skilled workers. This shortage is the most serious constraint on the country's economy.

Although its most far-reaching recommendations are likely to fall victim to politics, the report, which cost almost half a million dollars, is one of the most comprehensive ever done on education here and offers a well-documented survey of the daunting task facing the country in the field of education.

The statistics it offers are not reading for the faint-hearted. In the next 20 years, South Africa's population is due to increase from 24 million to 43 million, of whom 20 million will live in urban areas. While white pupils will increase from 860,000 to 960,000 in 1885, they will decrease to 760,000 by the year 2020, the report said.

It is estimated that black pupils, who now number 4.5 million, will be 8 million by 2020. In the same time period, 10 times as many black teachers (245,405) as white (24,981) will have to be trained if the report's recommended ratio of 30 pupils per teacher is accepted.

Although the number of black high school graduates has increased 100 percent in the past two years, more than half the black pupils drop out of school by grade six.

Already the government is attempting to close the gap by increasing its expenditure on black education, which went up 51 percent in the latest budget.

Blacks have long regarded their education as inferior to that offered whites because almost 10 times as much was allocated per capita to whites as to blacks. This was a primary grievance of rioting students in 1976 who viewed their inferior schooling as an attempt to keep them politically and economically subservient.

More than once, the report confirmed the "manifold and serious" disparities between black and white education. To correct them, the report recommended compulsory education for all races for nine years, the first six of which would be free. It also urged parity in government spending for all racial groups "in as short a period as budgetary, manpower and other constraints will allow."

The report especially urged that all universities be allowed to open their doors to all races if they wish. This has long been requested by the business community, which says it cannot find enough educated blacks to fill the jobs it has to offer.

Instead, Parliament this week established another all-black university to be set up in Transvaal Province.