My oldest is 13, 5'9" and 135 pounds. He is officially taller than both of his parents. To make matters worse, when he went for his well check, they told me he is about to have his growth spurt. He is wearing an 11.5 sneaker. So, he needed new jeans, I told him 2 pairs and wash often as we will need to replace in a few weeks anyway.
This is what we have done the past few years with DS15. We buy 2 or 3 pairs of jeans-which I have FINALLY convinced him he can wear more than once. We just got him some 29x34's online (can't find them in the stores). His feet have stabilized at a size 12 for about 6 months or so. Hopefully they are done growing. I haven't measured DS for a while but him standing next to Dad, who is 6', I am guessing he is about 5'10" now.