In our senior year, my deskmate stayed one extra hour every night to tutor me

At the midterm of the first semester of senior year I was fifth from the bottom of the class, and I had failed math.

The homeroom teacher called me into the office. He wanted to move my seat, up beside the podium, where I could be "kept an eye on." I said it was my own problem and there was no need. He looked at me for a moment and said, "It isn't about watching you. It's about watching your deskmate. He's first in the year and steady. Sit the two of you together and he won't be affected. You might be."

My deskmate was Cheng Yuan. Thin, glasses, never lower than the top three in the year in math. When word got around that he was being paired with me, my face burned. Overnight I had gone from "classmate" to "person in need of assistance," and a teenage boy's pride does not survive that intact.

Cheng Yuan behaved as if nothing had happened. On his first day he pushed half his notebook across the line down the middle of the desk. "Use it. I organized it. Mark anything you don't understand and I'll explain it during evening study."

From then on we had an appointment that nothing could cancel: one extra hour after evening study ended. When the classroom lights went out, we carried our little stools to the end of the corridor and worked under the streetlight and the green glow of the emergency lamp. His method was strange. He never gave me the answer. He only asked, "What do you think this step should do?" When I got stuck he waited. I lost my temper once and threw my pen across the floor. "Stop waiting. Just tell me the answer. I'll copy it." He picked the pen up, put it back in my hand, and said one sentence. "A copied answer won't sit the exam for you."

That hour was an hour he could have spent on anything else. He was already close to a recommendation place, and after evening study he was supposed to be memorizing vocabulary and drilling listening. He gave the hour to me anyway, every single day, from November to June. More than two hundred days. Only later did I learn that his listening score dropped that year. He had traded his headphone time for my functions and my geometry.

In June, the exam. My math came in top ten in the class, and my total scraped over the line for a key university. The day the results came out I went to find Cheng Yuan and started crying before I had finished two sentences. He handed me a bottle of soda. "What are you crying for? I didn't give you that score. You ground it out one problem at a time."

University took us to different cities. For four years I visited every winter and summer break, and I always brought the same thing: a box of mung bean cakes he couldn't buy in his hometown. During senior year he ate a dry steamed bun every evening to hold off hunger, and only when he had done well on a test would he allow himself the cakes. I caught him at it once, and he was embarrassed for a week.

One hour when you are seventeen outweighs ten thousand polite sentences when you are grown. He gave you the most expensive thing he owned, which was time, and now you owe him for the rest of your life. It is a debt you pay slowly, and gladly.

Now we live in our own cities and we both have children. Two years ago his daughter hit a wall in middle school math, and he posted in our group chat: "Which of you did I tutor back then? Give me an idea." I sent back his own words from the corridor. "Let the kid work out what this step should do. Don't hand over the answer."

He replied with a smiling face. "Learned something."

I looked at that smiley for a while, and then I was back at the end of the senior-year corridor: one lamp, one small folding stool, one problem we had not cracked after a whole evening of trying. It is one of the brightest lights of my life, and it was borrowed from a building that had already turned everything else off.