Teachers told Tan Chaoyun that they would have difficulty telling her six-year-old sons apart when she registered them at the local primary school.
Worried about mistakes and embarrassment (!) she shaved the large numbers into the hair of each of her boys before they started school.
"My sons are identical, even to me," says Tan. "I could only tell the difference between them by having different ankle tags on them before they turned 18 months old.
"Their father even now can't tell the differences among them. Sometimes he would punish the 2nd one for the 3rd one's mistake.
"Teachers and classmates can't get confused with the big marks on their head!"
Can you tell them apart? Britain's only identical quadruplets start school