The class and I brainstorm together ways that we will know what a “just right book” is. We discuss that we should know what most of the words mean, but we also mention that we should be able to think while we read. This type of metacognition makes sure the reader understands what he/she is reading.
The “five finger rule” is also a good policy to use. We read through a page and we raise a finger for each word we don’t understand. If by the end of the page, we have only raised one or two fingers, the book is too easy. If we have raised five fingers, the book is too difficult. If we have raised three or four fingers, the book is just right.