JOHANNESBURG, NOV. 3 -- The South African government, in a major reversal of its segregation policy for public school sports events, has proposed forcing schools that do not want to compete against teams with blacks to withdraw from mixed athletic events.

Under existing policy, it is the teams with black members that must withdraw if any objection to racial mixing is raised.

If the proposal survives a review by local school advisory groups and a strong challenge by the far-right Conservative Party, it will represent the most fundamental shift yet toward nonracial sport in South Africa's public schools, and, in effect, will penalize white schools that refuse to compete against blacks.

Education sources said today that the draft policy was an outgrowth of a major controversy last February over the banning of a popular Natal Province black high school track star from a national athletic competition in Pretoria because of his color.

The banning acutely embarrassed the government of President Pieter W. Botha, which frequently cites integration of professional and amateur sports outside of public schools as evidence that South Africa is making progress toward eliminating the apartheid system of racial separation.

The Ministry of Education and Culture refused today to comment officially on the proposal, saying that it was still under review by advisory bodies and required final approval by the government. A ministry spokesman said it was "premature" to discuss the reform proposals.

Government education sources confirmed, however, that a three-page policy document containing the changes was discussed last week by education councils of South Africa's four provinces, and that at least two of them -- Natal and Transvaal -- had approved the proposals.

It was not clear how the proposals circumvent South Africa's amended, 1983 constitution, which stipulates that athletic competition in schools falls under the category of "own affairs" and may be controlled by local option, while sports outside of schools come under "general affairs," which are governable by central authority.

Conservative Party leader Andries Treurnicht condemned the change as "forced integration" and suggested that the right-wing opposition in Parliament would fight school sports integration.

"It has become clear in recent times that there is a new form of racial discrimination against those who wish to exercise their freedom to associate or not to associate. It now seems that if they {white sports teams} want to take part, they will have to toe the line," said Treurnicht.

The Conservative Party holds 22 seats in the 178-seat white chamber of Parliament, which is controlled by Botha's National Party.

Roger Burrows, education spokesman for the liberal opposition Progressive Federal Party, said that the proposal appeared to represent "a fundamental shift, a real advance, in the acceptance of nonracial sport and will, we hope, be followed by advances in the acceptance of black scholars and students in all activities."

Enrollment in South African public schools is strictly segregated by race, and Botha's government has made it clear that it has no intention of changing that policy.

Segregation of school sports became an issue of national debate in February when the Kearsney College High School track team in Natal withdrew from a national schoolboy sports competition at Pretoria's Menlo Park High School because of the latter's objection to the presence of a 17-year-old black youth, Nkululeko (Squeegee) Skweyiya, a provincial track champion.

The dispute triggered a wave of protests by leading South African sports administrators and liberal members of Parliament. Critics said that highly successful efforts over the past decade to integrate amateur and professional sports in hopes of reducing South Africa's isolation in international athletics had been set back by the banning decision.

John Kane-Berman, director of the independent South Africa Institute of Race Relations, said today in an interview that the government had done "what any intelligent person would do if they wanted to move in the right direction.

"Let's hope that it goes foward. The fact that they are coming closer to the 20th century is a positive step," Kane-Berman said.