I would endorse the suggestion to use CS Lewis. His work is really good. “Is Theology Poetry” is one of his best, but might need HS level kids.
http://augustinecollective.org/wp-content/uploads/2016/06/1.2-Is-Theology-Poetry-Reading.pdf
Religion and Rockery is really great, and would work even for younger kids.
http://scientificintegrity.blogspot.com/2010/04/religion-and-rocketry-by-cs-lewis.html
Also take a look at Pensees by Pascal. It is really interesting. Also, it comes in short bites. For younger kids, you could read just one aphorism (about a paragraph or two), and get enough for serious thought.
https://www.gutenberg.org/files/18269/18269-h/18269-h.htm
See for example:
Blaise Pascal, Pensees, Section 7, 547. We know God only by Jesus Christ. Without this mediator, all communion with God is taken away; through Jesus Christ we know God. All those who have claimed to know God, and to prove Him without Jesus Christ, have had only weak proofs. But in proof of Jesus Christ we have the prophecies, which are solid and palpable proofs. And these prophecies, being accomplished and proved true by the event, mark the certainty of these truths and, therefore, the divinity of Christ. In Him, then, and through Him, we know God. Apart from Him, and without the Scripture, without original sin, without a necessary mediator promised and come, we cannot absolutely prove God, nor teach right doctrine and right morality. But through Jesus Christ, and in Jesus Christ, we prove God, and teach morality and doctrine. Jesus Christ is, then, the true God of men.
Dr James Tour and the Great Pascal
This last one is great to pair with radiocarbon dating of the Isaiah Scroll (see here https://journals.uair.arizona.edu/index.php/radiocarbon/article/viewFile/1537/1541), which I explain here Dr James Tour and the Great Pascal.
The strength of CS Lewis and Pascal, in my view, is that they are much more theologically grounded than most in the “apologetics” general. The one contemporary classic I would include, especially for Jr High and above, is More than a Carpenter.
https://www.amazon.com/More-Than-Carpenter-Josh-McDowell-ebook/dp/B002OFAY6O
This last one is particularly important, IMHO. It is critical to give kids grounding in the Resurrection and in Jesus, which is what this book does. The last reccomendation some people will dislike, but as an Indian I thought it was good. The Lotus and the Cross by Ravi Z., a conversation between the Buddha and Jesus.
https://www.amazon.com/Lotus-Cross-Jesus-Buddha-Conversations/dp/1601423187
In general, I think the work that focuses most on Jesus is the best. The work that is grounded in solid theology is best too, and particularly hard to find in our world. The best of all are rooted in stories. Thinking about stories, it is worth pairing these with CS Lewis’s novels, which he personally viewed a apologetics. For example, The Space Trilogy pairs really well with Religion and Rocketry. Till We Have Faces is considered a true masterpeice, and pairs well with the Myth the Became True.
Hope that helps. Great question.