Baltimore Catechism a good plain vanilla reference. Note also that there is a book called Scripture References for the Baltimore Catechism. Homeschool students, interfacing always with fundamentalists, must have their scripture in mind.
Catechesis of the Good Shepherd, a work based on the ideas of Maria Montessori and on lots of practical work in schools and parishes. Insightful. For me, the most helpful insight was that for really small children, the single most touching story is the story of the Good Shepherd. They identify with the sheep. Her second choice of scriptures, however, was even more surprising metaphors for our relationship with God and his life in us that he is light, that he is a candle in the heart, etc. "Bible stories" all those Old Testament stories with ambiguous and confusing relationships are, as my experience confirms, very confusing for small children.
The Early Reader's Bible as told by Beers and illustrated by Terri Steiger is a pleasure for new readers. It's out in two editions, and neither has what I would call beautiful illustrations, but the Steiger ones are much better than the other. This recommendation does not change what I said above. If you have a really early reader, find something else.
The Picture Bible a "cartoon" version caught my children's interest and got them familiar with the basic stories and characters. How nice to have children so you can find the resources you need to fill up the cracks in your own education!
Imelda, Patron Saint of First Communicants This is the story of Imelda Lambertini, one of the youngest of saints. Everything by Mary Fabyan Windeatt is very good; she probably has 20 saint books.
Sixty Saints for Boys and Sixty Saints for Girls by Joan Windham are delightful.
The Lion, the Witch and the Wardrobe by C. S. Lewis is en effective illustration of the concept of the Atonement. All the Chronicles of Narnia are very good. The videos are different. The cartoon videos are worthless. The acted version of "The Lion, the Witch and the Wardrobe" was enjoyable, -- I loved the beavers -- but the rest of the videos are scary and put too much emphasis on the witchcraft. Disney's Lion King is merely an attempt to steal the thunder from Lewis. The theology is very poor, as one might expect, but many still underestimate the effect on a small child's formation.
I have never seen a religion text that I really like; the Faith and Life series from CUFF is clear and good and has excellent illustrations, but is somewhat stiffly conservative. The Image of God series is softer both in style and alas! in theology, but mostly good. The other stuff on the market -- you're better off with Mother Goose.
Level II
The Bible. RSV is excellent. I love the Jerusalem Bible, but not the New Jerusalem Bible. Avoid any translation that says "new" because it almost always means inclusive language.
The Catechism of the Catholic Church. You must have this basic reference in your house.