Billkds, a user of Sina micro blog, posted on Sept 2 a photo of an apology letter on his/her micro blog, which he/she said was written by a student in a middle school in Shanghai, who was required by her Chinese teacher to write an apology of 800 Chinese characters, because she spoke in Shanghai dialect during the class.

The letter read, "I am deeply sorry that I answered your question with Shanghai dialect on your Chinese class and thus disrupted the class. … I made so a serious a mistake, and made you spend nearly 30 minutes on the class to emphasize the issue."

The teacher had allegedly came to Shanghai from elsewhere.

The message soon was spread and resulted in heated debate on the Internet. Some indicated that the incident happened in the Shanghai Minhang High School, and asked for an apology from the teacher.

However, a woman who claimed to be from the school's principal office said "there's no such thing."

"The school has investigated its Chinese teachers," said the woman who declined to be named, "Some said it was a first grader. Some said it was a second grader. But primary investigations show such things didn't happen."

According to the Daily Behavior Instructions for Students of Primary and Middle Schools issued by the Ministry of Education, primary and middle school students should speak Putonghua at school.

Shanghai Municipal Education Committee said, the city's policy is to advocate Putonghua while preserving the local dialect, and that the city should balance itself between the two, the Oriental Morning Post reported in April.