Another perspective:
It may be we're asking too much for someone so young to become quickly adept with a traditional riflescope, regardless the magnification or eye relief?
My thinking is it may be better to start them out with a red dot optic (personal preference being a Burris Fastfire), while teaching them to hunt with close-range opportunities. Unlike the traditional scope, eye relief, cheek weld, etc. are of little consequence.
The initial focus can then be more on just learning how to hunt and make clean kills instead of the more technical aspects of scope usage.
Along with this, practice target shooting with a traditional scope on a .22 (or even an air rifle). Over time, they will become more adept with using that traditional riflescope, and can "graduate" to it with the hunting guns.
The best answer to the original question may be just TIME
as he will learn how to use the scope over time.