Generally I don’t go by height alone when fitting juniors. I basically fit them the same way I fit an adult, finding the length and weight of club that allows them to swing the club comfortably so they can develop proper mechanics. That being said, Ralph put together a chart in the original Golf Club Design, Fitting, Alteration and Repair book for juniors based on height and weight. it cold be a reference or starting point, but I still feel just observing and looking at what club length ‘Looks right” for the junior is the way to go. In the chart, for a 5 foot boy Ralph suggests a driver in the 38″-40.5″ range and a 5 iron at 32.5″ – 34.5″. I thin those might be a little short, but without seeing the junior, hard to know. I think starting a little longer than that. You simply do not want to see the junior having to lift the club because it’s too long or too heavy. If you are going to build the clubs, before you decide on the exact length and put the the grip on, cut a 6 or 7 iron to a length and have him address it, if it looks right, start from there. Women’s standard lengths with graphite shafts on a #6 iron are now 37.5″, steel shafts it’s 37″. My guess is if you start at 36 – 37″ on a #6 iron it will be long enough to start and give you some room to cut down if it is too long. Aain, and the most important thing is that he can swing the club without struggling because it’s either too long or too heavy.