15- 16 years old. According to the standard of children's age, 1 to 3 years old is infancy, 7 years old is preschool, studying and playing in kindergarten, 7 to 12 years old goes to primary school, 12 years old graduates from primary school and goes to junior high school, and then two years later, it is about 15- 16 years old. So junior high school students are 15- 16 years old.