How to divide junior group A and junior group B in traditional school track and field competitions?

Juvenile groups are generally groups under 16 years old. Since they are divided into juvenile groups, they are generally not divided into groups A, B and C according to their age. Even if they are divided again, they are divided according to their professional level. For example, Group A is a traditional school group, Group B is a sports school group, and Group C is an ordinary school group.

If middle school students are divided into groups A, B and C, then generally: Group A is over 16 years old, Group B is 14-16 years old, and Group C is under 14 years old.