From 8:30 a.m. to 9:00 p.m., 12-year-old Zhao Di spent all of Saturday in a private tutoring center studying Chinese, math and English. It was the busiest, most exhausting day in his week.
Zhao studies at a private middle school in Zhengzhou, capital of central China's Henan Province. In his class, almost everyone takes tutoring classes outside school on weekends.
For Chinese parents, private tutoring is not just a supplement to school classes, but a necessity.
In 2016, more than 130 million private tutoring courses were taken by primary and middle school students in China, said a report by the Chinese Society of Education.
More than 87 percent of Chinese parents consider private tutoring programs important for their children, according to the report.
In China, people believe that if their children can go to good schools, they can have a bright future. Many believe that parents' preference for prestigious schools has contributed to a boom in tutoring organizations.
Junior middle school entrance examinations are forbidden by the Chinese education authorities, but the policy has not been fully implemented, especially by some prestigious private schools.
Tests for top middle schools sometimes go far beyond the primary school curriculum, so students have no choice but to take extra classes outside school.
"In the second semester of the sixth grade, some students only attend two or three classes at public school. The rest of the time is spent at tutoring centers, which promise parents their children will be sent to prestigious schools," said Shi Meng, a senior executive of the Jinsha Primary School in Zhengzhou.
Chinese parents are spending more of their savings on tutoring schools, too.
More than 30 percent of parents are willing to spend -- no matter how much it costs -- for private tutoring programs, and 26.6 percent of them are willing to spend half of their disposable income on these programs, according to the report.
For Li Jian, whose son is in fourth grade, the private tutoring fee is a great source of pressure. Every year, he spends an average of 30,000 yuan (around 4,500 U.S. dollars) on his son's tutoring, which is a lot considering the fact that he works as a driver and has to pay rent for his apartment. But he does not regret it.
"No matter how hard it is, he has to take tutoring courses so that he will have a better future," said Li.
The huge demand has helped tutoring companies thrive in China. The market size for tutoring organizations targeting primary and middle school students exceeds 800 billion yuan, according to the report.
Take the Tomorrow Advancing Life Education Group for example. When Zhang Bangxin, the group's founder, was in university for his master's degree, he worked as a family tutor to earn some extra money and realized there was a huge market.
In 2003, with 100,000 yuan in funds, Zhang founded the Xue'ersi International Education Group. In October 2010, just seven years later, it was listed on the New York Stock Exchange. In 2013, the group changed its name to Tomorrow Advancing Life Education Group.
Now the group has become one of the largest tutorial organizations in China with over 20,000 employees. Tutoring programs from the group now reach 37 cities in China, with 4 million offline students and more than 35 million online registered users.
Still, more newcomers are emerging.
Duan Chengcheng, who has years of experience in English language tutoring, just opened her own tutoring school on Dec. 2 in Shenzhen, one of the most prosperous cities in China.
Duan's English Language Tutorial School focuses on children ranging from five to 12 years old.
Although she did not do any publicity, five children have enrolled, and up to eight students are expected to come in spring next year.
"I want to keep my school small but with good teaching quality," said Duan.
"I love children and I love teaching. I believe I have made the right choice to bring more opportunities and help realize my dream," she said.