1. The Lion, the Witch, and the Wardrobe (1950)
2. Prince Caspian (1951)
3. The Voyage of the Dawn Treader (1952)
4. The Silver Chair (1953)
5. The Horse and His Boy (1954)
6. The Magician's Nephew (1955)
7. The Last Battle (1956)
While these are the most famous, he also wrote other works aimed at younger audiences, such as:
* The Pilgrim's Regress (1933), an allegorical novel for young adults
* The Great Divorce (1945), a religious allegory for adults, but with elements that appeal to younger readers
So, depending on how you define "stories for children," the answer could range from seven to more, depending on how you include other works with child-friendly elements.