At first glance, it looks like an ordinary gym class at a public school in Yibin, a city of about a million people in southwest China's Sichuan province.
But then you notice that the students are wearing signs: "Nitrate," "Sulfate," "Phosphate." In their game of tag, they chase the classmates they need to start a chemical reaction.
This is how gym and chemistry classes are combined at the Cold Water Well Middle School. Upstairs, in a combined history and math class, students use statistics to find patterns in the rise and fall of nations.
These experiments are the brainchild of former journalist Zhang Liang.
"What we're trying to tell them is that the real motivation behind all your studies is to help you realize how fascinating this world really is," he explains. "Once they get this, their own initiative will gradually emerge."
Zhang's experiments are hardly an isolated phenomenon. From Confucian-style academies and home schooling to foreign Waldorf and Montessori models, a grassroots, alternative education movement is blossoming across China at the secondary level. Universities and colleges, meanwhile, remain under tighter government control.
Education professionals are hopeful that these new teaching methods will benefit both public and private school students and produce future generations of Chinese young people who are curious, self-motivated and independent critical thinkers.
Zhang Liang, 47, speaks quickly and softly, with an intense gaze that darts out from behind his wire rim glasses. His inspiration to go into education came from what he witnessed during the devastating Sichuan earthquake of 2008, which killed nearly 70,000 people.
He noticed that mental strength and resilience were often a matter of life and death, and became determined to put humanity and humanism back into education, in order to prepare students for life's challenges.
The problem with China's current educational system, Zhang says, is that the way academic subjects are divided up severs the logical links between them.
He says the whole system is too focused on accumulating knowledge, passing tests and following orders.
"This makes students feel that studying is meaningless and boring," he says, sitting in a classroom at Cold Water Well. "They have to have some strong external pressure to move them forward."
Once the students' curiosity is ignited, Zhang's hopes are that students ultimately can design their own courses of study, assign their own tasks, and make their own rules. This is already happening at a private high school in the neighboring city of Chongqing.
The kids at Cold Water Well aren't ready for that yet. They're younger — in grades six through nine — and of the some 600 students, more than half are the children of migrant laborers who have gone to work in other cities.
But the new teaching methods and philosophy have turned the school around, says Vice Principal Wu Ge.
"When these kids entered the school, we ranked near the bottom of our district in terms of test scores," he says. "Three years later, they're graduating, and we now rank first."
Zeng Liang, an eighth-grader at Cold Water Well, remembers how she was so afraid of giving a wrong answer in class that her hands used to shake. But here, she doesn't need to worry about that.
Instead of listening to a teacher's lecture, the kids divide into groups, do their own research using tablet computers, and discuss and debate their findings.
"When we were little, we all studied on our own," she recalls. "There was no enthusiasm, and we didn't dare to speak our minds. Here we discuss and share our opinions. Now I stand up and speak, whether I'm right or wrong."
Only a few decades ago, China had a Soviet-style education system. The state assigned college majors and jobs based on what the state needed, not what the student wanted. And some subjects — like English — are taught the old-fashioned way, by repetition and rote memorization.
But in the past two or three years, Zhang Liang says, local governments have given schools some leeway to try new things. Although the government retains nominal control over curricula and teaching plans, Zhang says they are tacitly allowing experimentation, or at least not interfering with it.
The implications are exciting, Zhang says.
"Look how active these kids are, how they discuss things as equals," he says. "Once that becomes habit, it will produce big changes in their values. They will lose their blind faith in the supreme authority of teachers, or of anyone else."
Zhang is aware that the independent thinkers he trains could have a rough time fitting into China's authoritarian system. So Zhang teaches his students how to navigate the political minefields of Chinese society.
"In the private sphere, you are the highest authority, and you decide everything," he tells them. "But in the public sphere, it's not all about you, and you have to regulate your behavior according to a set of public rules."
This is a novel approach in China, where students are seldom told what rights in the private sphere the government can't touch, and what activities in the public sphere citizens have a right to participate in.
Zhang says Chinese authorities haven't completely realized the impact these reforms could have on their authoritarian system. They're too busy trying to cope with sweeping shifts in both social attitudes and demographics. And this is what is driving the changes.
China's population is aging. Schools have to compete for a shrinking number of students by providing more individualized instruction.
Secondary education has become a buyers' market, Zhang says, and parents with kids in both public and private schools are increasingly aware of their rights as consumers.
"School principals tell us that they're getting more and more pressure from parents," Zhang says. "Parents are starting to intervene when they feel that the school is treating their kids like cramming and testing machines."
As a result, the number of students taking the high-pressure national college entrance exam has dropped to new lows in Beijing and other cities, as parents send their kids overseas for study or choose alternate paths, such as homeschooling or vocational education.
The government responded in 2014 by allowing students to choose three of six subjects to be tested in. Before, students were only tested in math, English and Chinese, and there was a strict division between students studying humanities and sciences.
Very few of Zhang's students have taken the national college entrance exam — he has been in the education business for only four years — but he is confident that based on their performance at his schools they should have no problem with it.
Zhang says his foray into the education business has seen its ups and downs. He says he's more suited to education than entrepreneurship.
But in order to popularize his methods, in addition to running three schools — the third is in Guangzhou — he has established a consulting company that custom-designs school curricula.
He has set up a network of regional sales agents, and he funds it with the help of angel investors who see education as a potentially lucrative new market.
It appears that Zhang Liang's bold experiments are about to really take off. By next semester, he expects to sign deals for 30 schools to adopt his educational model.