JOHANNESBURG, NOV. 5 -- Black students demanding a boycott of final exams to protest school conditions clashed with pupils who wanted to take the tests, leaving up to 19 people dead, police said today.

Ten more blacks were killed in other township violence, including eight apparently caught in a feud between competing taxi companies, police reported.

The student violence in Bekkersdal, outside Johannesburg, began Thursday and lasted through the weekend. It was unclear if all 19 deaths were the result of student clashes, but police Capt. Eugene Opperman said he believed most were.

According to police, students opposed to the year-end exams had been trying to prevent other students from taking the standardized tests, which determine whether students may proceed to the next grade or gain admission to universities. Last year, less than half of the black students passed the tests, compared with a pass rate of more than 90 percent for white students.

The white-led government spends five times as much to educate a white pupil as a black pupil in South Africa, and anti-apartheid activists have complained for years about problems in the black schools.

Opperman said not all the people involved in the Bekkersdal clashes were students. He said one body was found today, but it was unclear when the person died.