The goal of sorting and classifying skills is to clarify thinking and improve their facility with language. Forming categories and dealing with their relationships is a part of logic. Sorting and classifying involve the recognition of attributes properties of a given object or group of objects person chooses to isolate and observe. Intellectural development consists in good part of learning to invent or discover attributes or categories relevant to a particular subject, then dealing with the relationships among various attributes. Through sorting and classifying the student can make better sense out of a wide variety of impressions and handle increasingly complex situations that might otherwise prove overwhelming. They can restrict information by choosing from among attributes, thus limiting the scope of any one problem to something that is manageable.
Buttons are great to start with because you can by a ton of them fairly cheaply and they have clear attributes to sort them by: color, size, shape, number of holes and as to whether they have shank or not.
You can then move on to any sort of object that is around the house; toys or natural found objects.
Once you feel sure that they are comfortable with sorting, you can move on to sorting trees.
Going back to the most familiar is the best way to begin using sorting tree, using buttons.
The tree begins with the first division, big and little. Each of these groups, then can be divided further into round or square under each of the size categories. Then the groups can be further divided by how many holes they have in them, under each of the previous categories. All these divisions form a tree-like formation.