Answer:
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
A home of wood in a wooded place, but built not by hand. High above the earthen ground, it holds its pale blue gems. What is it?
Sleeping during the day, I hide away. Watchful through the night, I open at dawn's light. But only for the briefest time, do I shine. And then I hide away. And sleep through the day.
I scribble forms of the finest letter, And repel elements of the harshest weather. I am an arrow-aimer and a dust-breaker.
What asks but never answers?
What covers its face with its hands, speaks no language, yet most known what it's saying?