Age not height should clarify who's still a kid

IT IS COMMON for children under a certain height to be able to use public transport and other public services for free. However, this practice is outdated because Chinese children enjoy better nutrition today. Gmw.cn comments:

In the past children did not get an ID card until they reached the age of 18. As a result, many children did not carry anything with them that could prove their age, and it was hard to judge children's ages based on their appearances.

Many park and bus management companies solved the problem by introducing the height standard, namely granting children under certain heights ticket exemptions. It was much easier to apply because all the ticket checkers needed to do was install a fixed ruler at a checkpoint.