Xue Zhaofeng, a professor from Peking University, reportedly has more than 170,000 subscribers to his online teaching course and could be making about 35 million yuan ($5.3 million) a year. Xue is only one among the hundreds of online teachers making millions of yuan a month. According to iResearch, an agency specializing in internet data collection, the online education market was worth 156 billion yuan by the end of last year, and it is expected to reach 260 billion yuan by 2019.

Online education has also found mention in this year's Central Government Work Report, which Premier Li Keqiang delivered to the annual National People's Congress. We can thus conclude that online education not only has huge economic potential, it also enjoys government support.

Online education has become popular because of the huge demand, and the entire market for providing training for primary and secondary school pupils is worth 800 billion yuan. There are reasons for that. The majority of Chinese parents attach great importance to education, and are willing to pay for extra courses to ensure their children's academic success. And parents who are willing to pay for such courses would also pay for online courses.

Moreover, intense competition in almost all fields in today's society has prompted people to gather as much knowledge as possible－for which they are ready to pay big amounts－to gain an edge over fellow contestants in exams as well as job interviews. According to 2016 Knowledge Youth Report, co-issued by several websites including guokr.com and 163.net, about 70 percent of online learners "paid for knowledge" last year compared with just 26 percent in 2015.

Online education has become immensely popular also because it conforms to the so-called 3E principle－everyone, everyday, everywhere－that is, everybody can study everyday everywhere.

Online education has some economic and other advantages, too. It helps people save time and money. One only needs to pay 200 yuan a year to attend the online courses of even a famous teacher, which is usually one-third of what the same teacher would charge for providing extracurricular lessons in person. To a large extent, it has also addressed the problem arising from a lack of quality education resources. Even an excellent teacher can share knowledge with a maximum of 100 students in a classroom. But the same teacher can teach tens of thousands of students online. This has forced some teachers to change their teaching mode, because the more popular they become, the more money they can make.

Online education is not without problems, though. Some online courses are to education what fast food is to cuisine, as they simply teach students some easy tricks, instead of imparting real knowledge. Besides, being popular does not necessarily mean a teacher is also good. Some online "educators" are extremely popular yet they hardly teach students anything useful.

Worse, there is hardly any supervision of online education agencies. The education law requires a person wishing to run an online teaching agency to register at the local education bureau. But a China Central TV report on Nov 17 said quite a high percentage of such agencies are being operated without the education bureaus' knowledge, because they register as technology firms in order to avoid supervision by such bureaus.

For the healthy development of the industry, education authorities should more strictly regulate the applicants and draft national standards. Also, online education agencies should know they cannot continue offering just simple and smart tricks to students to clear their exams, and instead have to offer quality education to students to succeed in the real world in the long run. And students should realize, no matter how useful online education is, it cannot replace school and college education.

The author is an associate researcher in education at Beijing Normal University.