One of the hardest things to demonstrate and teach is how tone or mood is developed in a poem. It is all wrapped up in things like word choice, meter, imagery, anthropomorphizing, dialogue, sonics, structure, etc., and is really hard to pin down!
Here are a few Frost poems that are super for demonstrating tone or mood:
“A Late Walk”, poem text here.
“Storm Fear”, poem text here.
“Now Close the Windows”