With China - the world's biggest market - such a short distance away, Malaysians regard a knowledge of Mandarin as an asset in business.
However, although many Puay Chai parents are professionals with Chinese origins, they were educated in English and do not speak Mandarin at home. Even fewer of them can write it - learning the 2,000 or so characters is a laborious process that needs to be started young.
The children worked from 9am to noon, every day. As well as studying Mandarin, they had classes in mathematics and singing. All classes were taught in Mandarin.
Puay Chai primary school's special programme has been running for three years. The 2,800-strong school had an intake of 590 children into Standard One this term. Of these, 400 had completed the optional four-week tuition course.
The teacher of one class of 40, Madame Saw Mei, said she finds that at first few of the children can write any Mandarin characters at all and she aims to teach them 30 or 40 before the course is over. They learn simple, basic words such as the names of colours and how to give directions.
Like the children, Madame Saw Mei seemed unconcerned at losing a large part of her holiday. "I don't mind," she said, "it makes it easier for them to catch up. It's good for the kids."