A student learns from an online open course in a middle school in Changsha, Hunan province on Nov 28, 2014. [Photo/CFP]

A physics teacher made 18,842 yuan ($2,890) in an hour for his online course, but educational authorities are calling for ban on this teaching model, according to China National Radio.

A total of 2,617 students have signed up for Wang Yu's tutoring course on high school physics, which is carried out online at a cost of 9 yuan for each audience member. The seven-classes have attracted 9,479 students in total.

With an online portal hosting the course charging 20 percent of Wang's income, the teacher made an average of 18,842 yuan per hour.

A college English teacher also using an online teaching platform said she she earned about 50,000 yuan in two months, with the largest class attracting 1,700 online students.

Online education services are mushrooming in China. One tutoring site offering eight middle and high school courses boasts 15 million registered student users. Online teachers are generally happy with the extra income because the Internet has greatly reduced travel costs and allows more flexible instruction.

"A computer with a camera will do, as long as the network is stable," Wang said.

Low costs and high efficiency of online classes have also attracted various parents.

"Compared real classes that cost one or two hundred yuan, online equivalents are available for less than 10 yuan. I prefer this mode if it helps my child," one parent explained.

But it has raised eyebrows among local educational authorities. An official from the Education Bureau in Nanjing, capital of east China's Jiangsu Province, said the city bans teachers from offering paid tutoring to students including online services.