Challenges is based. The problems are not only challenging, but fun. That, too, is by design. Higher-level mathematics can be as daunting to parents as it is to students, particularly for those parents who may have struggled with mathematics when they were young. Which is not to say that the strength of the problems has been diluted.
Challenges offer families two additional benefits.
First, they illustrate to parents what their children should know. This can be an important, albeit sobering, revelation for parents, leading to their becoming more involved in their children's mathematics education. We forget that every child's learning begins at home. From learning to talk, to learning colors and the alphabet, to counting, to nursery rhymes and stories, children begin learning as babies. And that learning comes from parents.