The speaker in "if everything happens that can't be done" has something against books, and he talks about a stupid teacher. He doesn't seem to be much of a fan of school. Really, though, reading and writing are important, but teachers, schools, and textbooks have a way of making them seem mundane and torturous. And the speaker of this poem, writer that he is, seems to know that. Go listen to a bird, he suggests, and forget about reading those books for a while. You just might learn something new.
The speaker in this poem prefers learning from the outdoors to learning from books, because the outdoors provides more knowledge.
"if everything happens that can't be done" shows us that true education happens after the school bell rings.