Pediatricians and family physicians use a growth chart to keep track of their patient's weight and height. The growth charts were developed from information obtained by measuring and weighing thousands of children. From these numbers, the national averages for height and weight were established. All dimensions of weight and height are given in percentiles, with the 50th percentiles being the average. In regular terms, this would mean that out of a 1,000 children 500 would be above the 50th percentile and 500 would be below the 50th percentile. It is important to remember that there is a wide variation in the height and weight of "normal" children. Most physicians consider a person's height or weight is in the normal range if it is between the 10th and 90th percentile.
For a 15 year old male the average height would be 67 inches (50th percentile) and the normal range would be from 63 inches (10th percentile) to 72 inches (90th percentile). The average height for a 15 year old female would be 64 inches with the normal range being from 60.5 inches to 67 inches.
Since the teen years is a time of rapid change it is very common for percentiles to vary to great extent from year to year. Ultimately your height has been predetermined by your genetic makeup and will stabilize near the end of adolescence.