that is a completely useless number.
the average 15 year old male can range from 5'0" to 7'0". most boys range between 5'4" and 6'2". Anywhere in that range can be considered normal. There are variations depending on race AND on geographic location.
Because males reach growth spurts at different times depending on genetics & environmental factors, the average height of a 15 year old is about the same as the average height of an adult human, but unlike adult humans, 15 year old males are not done growing (growth plates for males close ~ age 19 or 20)