A new student protest against black education erupted today in Johannesburg's black township of Alexandria when riot police used tear gas to disperse hundreds of youths who walked out of classes and took to the streets to demonstrate.

Students streamed from classrooms this morning and marched toward a central square in the township. They waved banners criticizing the quality of black education and calling for the release of two youth leaders detained by security police last night. Authorities apparently arrested the two Alexandra Student Council leaders after receiving a tip about the protest.

Alexandra is a black area with a population of about 20,000 located on the outskirts of Johannesburg's post white northern suburbs.

Although less than a tenth of the size of Soweto, this city's main black township, Alexandra's proximity to the white areas always has a greater impact on whites.

The double standard of education for blacks and whites is one of the main complaints of the black youth movement and has triggered several school boycotts and disorders in Soweto since the first unrest more than a year ago.

The issue has reached such a peak that students have put pressure on black school board members and teachers to resign, and school buildings have become targets for arsonists. Six schools in Soweto have been damaged in recent weeks.

The president of the Soweto Students Representative Council. Trofomo Sono, announced over the weekend that teachers would be given until the end of the year to "do something about Bante (black) education - otherwise some of them will not have schools to teach. School board members in many black townships have been given until Wednesday to resign and several already have.

The latest wave on unrest began yesterday when an estimated 30,000 black pupils from 29 schools in Pretoria's African townships of Atteridgeville and Saulsville walked out. Teachers said the boycott was triggered by a group of youth leaders who traveled from school to school, urging pupils to leave and join the protest.

One Atteridgeville student explained: "Leaders feel that the only way to get some reaction from the authorities is to stop going to school until systems change."

The boycott in the Pretoria area continued today, although police - who roamed the township in unmarked cars - reported no violent incidents. Student council leaders have pledged to keep the schools closed until the current curriculum is "replaced with a more acceptable type of education."

The protest appears to be spreading to include other areas of discrimination. Students in Attridgeville yesterday warned drivers of black "second-class" taxis that they must remove their "non-white" signs or face trouble.

Many shopkeepers closed their doors today, responding to the protest. Some claimed they were afraid of violence. Others said they thought it a "good time to show sympathy with the students," a statement indicating the growing influence of the militant youths.

Although officials reported tonight that the situation in both Atteridgeville and Alexandra was under control, there is growing fear that the spread Wednesday. Students in Soweto returned from vacation July 19 and there have been rumblings among youths ever since.

Officially, the government is in a weak position to argue the importance of the issue, despite the claim by education official F. J. Wiese that criticism of black education is Communist propaganda. During almost a year of inquiry into the unrest by a one-man government commission, the most recurrent motive given for disorders has been the inferior standard of black education. For example, schooling is not compulsory for Africans, while it is for whites.

The white administrative board for Soweto recently announced plans to build more than 10 schools and vocational centers for blacks - an obvious response to the protests. The students, however, immediately balked at the offer with what has become their standard response: "too little, too late."