It's about costs, it is very expensive to attend those private classes. And if other kids are doing it, some parents may have to do it as well. From the stories

It's about costs, it is very expensive to attend those private classes. And if other kids are doing it, some parents may have to do it as well. From the stories, the gov't may provide some mooc-like platform for students to learn more subjects. Like many developed countries have done, birth rates boosting is often hard to achieve.