Whose only play was what he found himself, (Line 26)
How many boys could live such an isolated life these days? In some parts of the word, this lifestyle is still possible. But most people might have a hard time relating to the life that Frost describes.
One by one he subdued his father's trees (Line 28)
The boy seem to enjoy conquering his father's trees. Is this different from the way an adult would appreciate a birch tree?
[…] He learned all there was To learn about not launching out too soon (lines 32-33)
This would be the best and worst school ever. You'd certainly learn a lot of lessons at once if you fell out of the tree, but it doesn't seem like it would be the most comfortable way of gaining knowledge.