Online teaching, where live-broadcast lessons are distributed through the internet, is quite a popular tool for many school students and exam-takers. News on how lucrative this can be for a teacher has attracted much attention and triggered a debate on the good and bad aspects of online teaching.

Physics teacher Wang Yu only teaches on the Internet. He joined an online education platform in 2015. Now he earns much more than ordinary school teachers, with a figure the latter cannot even dream of.

A 45 minutes live broadcast lecture of Wang costs nine yuan. He usually has more than 2,600 students sign up for his lecture. Wang earned 18,000 yuan (U.S.$3,000) in less than an hour.

There are a lot of merits of online education. For students, it Is cheap, interactive, no location concern as long as there is wifi, and you can always re-play the lecture. For teachers, they earn more. That explains why it booms.

“There are 220 million primary school students across the country. There’s a huge demand of online education,” said Jiao Yabo, founder of an online education platform.

And another foreign language online learning institution got a surging registered members in 2015, six times more than the number of the previous year.

“We have more than 97 million registered members on our platform, 70 million of the users use their mobile phones, it grew rapidly in last two years,” said Fu Cairui, founder of an online education platform.

Some say this reflects current education problems such as underpaid teachers, uneven distribution of resources, and high school fees. But there are also voices questioning the quality of online lectures and teachers’ credibility.

Some education experts suggest that online education system should be applied to public schools. But so far it is still a gray area now under the spotlight.