As a wordless picture book it is easy to have students write the words to tell the story.
Making connections is a great way to get readers thinking about the story. Discussing what they would use the magical chalk to create and explaining why they chose it. Another open ended question is, would you leave the chalk behind again explaining why or why not.
This book can also be used to discuss cause and effect the relationship between the drawings that are created and the effect they have on the kids.
Students can judge who drew the most important illustration and establish criteria for what constitutes a good drawing based on the circumstances.
Have the students write a sequel to the story - what would the characters do after leaving the chalk on the playground.
I love covering the title, and having my students create and evaluate the best title for the story. Sometimes I show the students the actual title at the end, others I encourage them to seek out the author and text, encouraging students that is' not always reading that helps your understand it's something to consider.
Wordless picture books are a fabulous part of primary classrooms and this is one of the better ones I've seen. The pictures alone are amazing. Plus it's always great when a kid can make up the story with the text!