Tick, tock, tick, tock Xu Xiangyu grew visibly unhappier with every second that passed. It was Saturday afternoon and his darkest moment was approaching.
By 6pm that day, the 11-year-old was seated alongside dozens of classmates in a school down a lane in urban Beijing. In front of him was a list of 16 mathematical equations. He had one hour to solve them.
Tick, tock, tick, tock
He failed and, one hour later, he sat silently listening to his enthusiastic teacher reveal the answers. From time to time, he could feel his mother's watchful eyes on him from several rows behind.
She had watched on, taking notes, as were other parents and grandparents who had come along to observe.
"Those questions were so difficult, even I don't know the answers," said Huang Yan, Xu's mother, who has a master's degree in communication. "I took notes in case he needs my help later."
The class was an "Olympic math" session, which aims far higher than the primary school level. There are also similar courses for English or Chinese literacy already widespread across the country.
For Xu, a 5th-grader, the lessons mean 36 extra hours in a classroom and, as he says, "personal torture". For his mother, it means a 1,600-yuan ($230) bill.
"What's the point of learning things that are useless in daily life?" groaned Xu, who spent a year at a primary school in London, England, from 2007 to 2008 while his mother studied there. "A question like 'What's the sum of the first 500 figures of 1,2,3,2,3,4,3,4,5,4,5,6?', do you think the question means anything in life?
"The class is like poison to me. I hate it."
Xu's mother did not agree, however. She said: "Almost all the kids in his grade are attending such classes. I am afraid he will lag behind if he doesn't. The competition for a good middle school is so intense."
For Zhao Zihao, a 6th-grader in Xinxiang, a city 600 km south of Beijing, two one-hour "Olympic math" lessons a week is nothing to complain about.
Zhao takes the class every Monday and Tuesday night, along with a two-hour after-school English class every Thursday and Friday night.
"I know he is tired but what else can we do?" said his father Zhao Qingyong. "We are from an ordinary family. He has to study hard to enter a good middle school."
China's nine-year compulsory education covers primary and junior high school, and no entrance tests are required. Students are assigned to schools depending on their residency, according to the Law on Compulsory Education.
But in reality, a pupil can be enrolled in another school, usually a good one, rather than the one he or she is assigned to, if the student excels at math or English or has a special musical or sports talent. A top award in "Olympic math" or English, for example, or a national certificate for piano would be a stepping stone towards a top junior high.
The other way would be through family connections with officials in the relevant authorities or a huge "voluntary donation" to a school.
These "donations" can vary widely. Zhao Qingyong said his son did not do well in a test organized by an agency representing a school he hoped his son could enter.
"I paid 50 yuan for the test, but the agency said the top 120 students could enter the school without paying donations," he said.
"I heard the donation for that school was about 18,000 yuan. But we need to find some guanxi (connections), otherwise we will not even have a chance to give the money."