How is the theme of categorization explored in Chapters Five through Eight?

The theme of categorization is explored through Dell's use of categories to separate his students. In these chapters, the author describes how Dell came up with his four categories, after which, he isn't required to do much more additional work, as his seesions involve nothing more than following a script based on what he thinks each child wants and needs based on the category into which he’d put them. The shortfalls in his system are uncovered when Willow comes into his office and he needs to create a new category because he is unable to fit her into any of the ones he has already created.