Boys do grow fast at that sort of age. 4-5 inches in a year is common during the growth spurt, though it does happen at different ages. One of our family pictures shows my father and brother together on Remembrance Sunday 1976, when my brother was two months past his fourteenth birthday. There he is still a good deal shorter than my 5ft 6 inch father. Two years later he was clearly taller, and is now just under 6ft. By contrast, I stopped growing at 14, when I was the same height as my father.
Ann