There are tons of books aimed at children that educate them on life's complexities. The most popular example is 'Harry Potter', which teaches children the importance of found families and hope during dark time. Along with that, there are other amazing series that are also wonderful educators, such as 'A Series of Unfortunate Events' (which teaches that life is not fair nor is it always happy, but the love you build and fight for is what makes it worth living) and— a personal favorite of mine— the 'Percy Jackson' series and its many spin-offs (which teach the same messages as the previous two and also gets bonus points for being FULL of representation of children who often don't get to see themselves as heroes; kids with ADHD, dyslexia, gay children, trans children, muslim children, so many different races and personalities, etc).
That being said, I think one of the most profound and important pieces of literature for children (and adults) to read is Phillip Pullman's 'His Dark Materials' trilogy (often better known as 'The Golden Compass' series).
Pullman tackles so many intense and important themes in this trilogy that it's hard to pick just one to focus on. What theme is most important for a child to gain an understanding of early in life? The dangers of blind religion, science for the sake of evil versus science for progress, found family vs blood family, anti-authoritarian themes, free will, aging?
For me, when I first read this series at age 12, the one that stuck with me the most was the last one. A lot of the series aimed at children instilled a fear in me of growing up. Specifically growing up and missing the time for the adventure to start. You get your letter from Hogwarts at 11, you get claimed at Camp Half-blood around age 13 and often don't live to age 18. The Baudelaires are surrounded by examples of well-meaning but incompetent and patronizing adults. Susan Pevensie hit puberty and was no longer allowed in Narnia.
For a child reading these books, I often felt like I was running out of time to do something great, to find real happiness and purpose. I feared puberty and the loss of childhood that would come from it. Adulthood was something to avoid at all costs.
Pullman directly fights against that theme. He has never hidden his distain for the storylines in 'Narnia' and how they frames adulthood and sexuality, particularly for girls. This theme is one created by the Christian belief, which Pullman is often very critical of.
In his story, which follows a young girl named Lyra, adulthood at first is something she fears. The adults in the story are self-serving and cruel, and Lyra fears the moment her daemon settles (the physical way of showing adulthood). As we learn later, many of the adults also fear this moment for the children, and aim to sever the children from their daemons in order to prevent Dust from settling in them. This severing process leaves the children stunted and soulless essentially, but the adults believe it frees them from sin (this is a parallel to genital mutilation).
A common Christian story about the loss of innocence is the story of Adam and Eve, and the Tree of Knowledge. Everyone knows the story, and knows that the Original Sin is seeking knowledge which made the couple learn shame for their naked bodies. In 'His Dark Materials' this is flipped. At the end of the booksLyra— who is called the 'New Eve'— and her friend and lover Will become the new version of Adam and Eve, after destroying the embodiment of God, with Lyra offering up Will fruit. This is a new start on the myth, this time with Eve as the hero. Pullman doesn't form this sexual awakening as something shameful, and is firm in the belief that seeking knowledge is not only necessary, but also something to revel in.
Lyra's story arc is in direct reaction to Susan's. The same sexual awakening that condemned Susan freed Lyra. Adulthood doesn't mean the end of Lyra's life, or bar her from anything majestic, nor does it take her wonder. Her and Will know what they are accepting, the Knowledge, and they go forth with confidence that the pain of life is also worth the freedom of knowing and loving consciously. Lyra's choice saves her world and many others, bringing the Dust back, restoring the natural balance. She resets the multiverse, allowing for a life where Knowledge can exist without sin.
This type of story was so important to me at the age I read it. I was scared and ashamed that I was aging, that I was close to puberty and adulthood. I feared that I would lose something beautiful and gain nothing, and that there was nothing I could do to stop it. So many stories for children (whether they mean to or not) push forward this narrative.
It was a pleasure to have an excuse to reread these books as an adult, now that I'm well past the point I once feared. I firmly believe that these books are a pivotal story for children— especially little girls— to read before they hit puberty. It doesn't shame children for aging, for becoming aware of their bodies, for wanting to know life as an adult. It revels in it, and give hope to any child reading (especially young girls, who particularly suffer in stories when they get 'too old') that adulthood isn't something to fear.
It can be scary and big and overwhelming, but the knowledge of adult life is something to cherish. Growing up is not the end, but a new beginning.