One teacher has been arrested and the other has fled, a policeman at the Weining County Public Security Bureau in Guizhou province said Tuesday. Like many Chinese officials, he refused to give his name.
Seven others are also in police custody while the case is being investigated, he said.
A teacher who picked up the phone at the Xinfa Township Middle School in Guizhou province and who said his last name was Wu told The Associated Press that coal mine owners paid the teachers nearly 5,000 yuan ($660; EUR480) for arranging liaisons with more than 20 school girls.
Some of the victims dropped out of school after they were raped, and those who continued will not talk to their classmates, Wu said.
The victims each received a gift of 800 yuan ($106; EUR78) on the June 1 Children's Day national holiday because of what happened to them, said an official with the county Communist Party Propaganda Department, surnamed Geng.
A man who answered the phone at the Weining County Education Bureau said he knew nothing of the case, and refused to pass the call to anyone else. He gave another number to call, which was continually busy.
Separately, the Ministry of Education issued a notice Tuesday forbidding schools from sending their students to entertainment facilities such as bars, karaoke parlors and bath houses for work experience.
Last November, a government-run dance school in Guangxi province sent girls to sleazy bars in Hangzhou, sparking an outcry in the media.
In a notorious case of abuse, two teachers were sentenced to death, in 2005 and 2007, for raping 9- and 10-year-old girls in a township in northwestern China.