One educator, one line, one true story.

Rita Pierson taught for forty years in low-income schools in the United States. Many of her students opened by telling her they were "not the type who could learn." In her 2013 TED Talk she told one small story that has since traveled through the education world.

A student that year failed a math test badly. By the standard rule his paper would have been marked "-18." She did not write -18. She wrote "+2" at the top and drew a smiley face. The student looked up and said, "Ma'am, this is a failing grade, right?" She said, "Yes, but you got two of them right. You are not everything wrong."

Her point later: "-18" tells a child, you are finished here. "+2" tells the same child, you have a starting point to climb from. Same child, same test, different words in the corner. Whether he opened the book again that week was not a matter of aptitude. It came down to the sentence.

A few weeks after her talk was posted, Rita Pierson died from illness. The video has since been watched over 20 million times.

Maria Montessori was Italy's first woman doctor. Assigned early in her career to a Rome mental asylum, she was asked to work with children other professionals had called "unteachable." She noticed something the others had stopped noticing. When given materials that fit their hands and their attention, these children would repeat the same task with great care, over and over. That observation redirected the rest of her life.

In 1907 she opened the first Casa dei Bambini (Children's House) in a slum tenement in Rome's San Lorenzo district, taking in fifty to sixty children aged three to six from families with no time to attend to them. Her method was almost embarrassingly simple: furniture built to a child's scale, materials the child could choose without asking, and a teacher whose main job was to prepare the room rather than to lecture in it.

Within months the neighborhood noticed. Children the district had written off as unmanageable were sitting still and working. They were putting things back. They were teaching each other. Within a few years, educators from across Europe were traveling to see the room.

In 1896 the University of Chicago hired John Dewey to chair its philosophy department. He accepted with one attached condition: he would open a laboratory school to test his own philosophy of education. This became the Laboratory Schools of the University of Chicago.

The school looked like no other of its time. Children learned mathematics by measuring in the kitchen. They learned history by learning to weave, because the history of textiles is a real thread of human history. They learned science by cutting wood in a carpentry shop and assembling what they cut. Dewey was not trying to raise a generation of chefs and carpenters. He was trying to demonstrate a single point: when hands are doing something real, thinking actually begins.

His wife Alice served as the school's principal. The school ran for seven and a half years. The children who came out of it later included elementary school teachers, lawyers, and scientists. Dewey himself acknowledged that those seven and a half years forced him to revise a great deal of his more speculative pedagogy. Not defeated, sharpened.

Tao Xingzhi went to the United States in 1914 and studied at Columbia University under John Dewey. He was a serious student, but he also saw something clearly: Dewey's phrase "education is life" worked in America but did not translate back to the China of that time. China then had 400 million people who could not read, most of them in the countryside, a world away from any classroom.

When he returned home, he performed an almost mirror-image inversion: he flipped Dewey's "education is life" into "life is education." Education was not to be a matter of dragging life into the schoolhouse. School itself had to be set down, so that education could grow inside daily life.

In 1927 he founded Xiaozhuang Normal School outside Nanjing. Students did not live in dormitories; they lived in farmers' homes. They planted, they carried water, they taught the farmers to read while they themselves studied pedagogy. In 1939, during the hardest years of the war with Japan, he opened Yucai School in Chongqing for gifted children who had lost their parents to the war. One line he returned to often: learning happens inside doing.

In the age Confucius lived in, learning was mostly walled off inside the aristocracy. Children of feudal households studied ritual, music, archery, and charioteering; the children of common families had almost no path to reading. What Confucius did, and what would have sounded near-offensive in his time, was to push that door open.

The Analects records this line of his: "If a person brings me even a bundle of dried meat as a first gift, I have never refused to teach them." A bundle of dried meat was the most basic token a commoner could bring. It was a floor set low enough that anyone motivated to learn could step over it.

Tradition holds that he taught over three thousand students across his life. Of those, seventy-two are remembered by name. Among them were sons of nobles, small traders, farmers, and students so poor that home barely had food. He did not sort them first and then teach. He taught first. The sorting was left to others.