Hi
As Geoffrey Taucer said this is very common, unfortunately it is totally avoidable, but it does require work.
Ok pre-requisites to be able to a straight inlocate, from the get go are:
1- Good swings (as always). Chest at least rings height (i assume everyone interested would know the correct technique for a proper back swing on rings)
2- Good shoulder flexibility, especially in abduction ( ranging in all planes)
3- Strong tap (this however a variable of pre-requisite 1)
So here is a kid with a good swing (i am assuming he has a good swing to be learning these, as otherwise if the approach is just do it, than advice is pointless).,, but pikes the inlocate why?
Common errors that cause the pike are:
1- early inlocate, an early inlocate kills the swing, and forces you to pike, because pressure is no longer applied to the rings..
2- and early inlocate also tends to cause the shoulders to round which kills the heel drive in itself (action reaction...so to speak) The two are dependant on each other
3- Head is not keep neutral
4- Rings are not pushed out to the side wide enough.. look at your son front on, and i am 80% that the rings are maybe about 20cm or wider than his shoulders in the swing.. This relates to correct back ring swing techniuque, which is vital... the chest mush push down, and the rings must! go out wide to allow the body to rotate faster and freely.
If you can film your son doing 2-3 goes, post it or email me/PM with it and i am 90% sure that i will be able to point out all the things above (the other 10% is the exception to the rule). (if you do send vids...try to film at least 1-2 front on attempts)
So in short, the quick fix to the problem is to have good enough swing technique before you actually start learning it, make sure they don't inlocate early, and once again swing technique and shape.
Hope that helps