By Daniel Griffiths
BBC News, China
There is huge pressure on Chinese students to succeed
Shanghai's largest taxi company is calling in all its cabs with the number four on their licence plates.
The firm says it is trying to boost students' chances in this week's national college exams.
Four is considered an unlucky number by many Chinese people, because the word four in Mandarin and Cantonese sounds like the word "to die".
In the past parents have complained about their children taking taxis with licence plates including the number.
Shanghai Dazhong taxi company has finally bowed to public pressure.
The college tests are the key to a university education in China, and parents and pupils do everything they can to increase the possibility of success.
With more than eight million students sitting the exam, competition is fierce and cheating is extremely common.
Last year, several teachers were convicted and jailed for selling test papers ahead of the examination day.