There is a joke that says airplane passengers bound for Chengdu, the capital of Sichuan province, can hear mahjong tiles clicking together before landing.

The joke suggests how popular the Chinese pastime of mahjong is in this southwestern city of 14 million people.

The game is now helping local students to learn English, thanks to the innovative work of a high school teacher.

Students at Jitou High School are playing mahjong in classrooms to memorize English words. Photos of them playing have become very hot online in recent days, with many netizens calling the inventor a genius.

Unlike normal tiles, those used by the students have English letters, from A to Z. Students try to form English words and sentences with the letters.

Tian Jingyun, 53, the principal and an English teacher at the school who created the special tiles, said that, for example, "the words can be China, future or eat, while sentences can be 'I am an engineer' or 'This is a big dog'."

The student who can form the most words or longest sentence using the 13 tiles in his or her hand wins, Tian said.

In 2000, while teaching Chinese in a high school in Seattle in the United States, he was impressed with how teachers instructed students in an entertaining way.

He realized that Chinese students lacked interest in English because they were primarily trained to take examinations. His idea that English is fun became the driving force behind his invention.

With a mahjong set, which has 108 tiles, Tian experimented to see how many English letters were needed in a set so that students could form words and sentences with 13 tiles. He noted the frequency of letters appearing in words and set the quantities of each letter differently.

"For example, there are six tiles with A, two with B, four with C and eight with I," he said.

One student, Xiao Haorong, said, "Learning with mahjong tiles as a teaching tool has fostered our interest in English."

Tian said: "Some students will take the entrance examination for senior high schools on June 13 and 14. And they play the English-learning mahjong to let off steam from time to time."

He said he found it unfortunate that local education authorities have refused to promote his English-learning mahjong.

"They are afraid it might remind people of gambling," he said.