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.