This article about libertarian themes in children’s literature is of interest to me as a middle school teacher, and as a person with libertarian leanings. I haven’t read any of Margeret Peterson Haddix’s work, but I know from long experience that Lois Lowry is a wonderful writer.
There is a libertarian undercurrent to the Chronicles of Narnia, as well, though with a monarchichal bent. Near the end of the The Lion, The Witch and the Wardrobe, CS Lewis describes the four Pevensie children, who become the Kings and Queens of Narnia thusly:
“And they made good laws and kept the peace and saved good trees from being unecessarily cut down, and liberated young dwarfs and young satyrs from being sent to school, and generally stopped busybodies and interferers, and encouraged ordinary people who wanted to live and let live.”
We could do worse, these days. And have.