A student reviews the curriculum of an online IELTS course. Chinese Internet companies have invested heavily in online education in recent years, but critics argue digital learning should supplement rather than replace traditional classroom studies. Each week more than hundreds of students from across China wait for Yang Tao to log on to his computer. The 30-year-old puts on his headset and turns on his camera, but not to chat with clients, family or friends. Over the two-and-a-half hours, he will deliver a lecture for the online course Writing for the International English Language Testing System (IELTS) streamed on YY, a Nasdaq-listed social media platform. The website provides courses that prepare students for standardized English exams that serve as a gateway to studying abroad. Dubbed the "IELTS young general," Yang is a language training pioneer who recently expanded into online education. Over the past year, domestic Internet giants have invested heavily in online education. Baidu, Tencent, Sina and Alibaba are among the heavyweights that have their own online education portals. The trend isn't limited to China either, with Google and Amazon also climbing aboard the e-learning bandwagon last year.