Sorting is a beginning math skill. It may seem that a big chunk early math is about learning numbers and quantity, but there's much more to it. By sorting, children understand that things are alike and different as well as that they can belong and be organized into certain groups. Getting practice with sorting at an early age is important for numerical concepts and grouping numbers and sets when they're older. This type of thinking starts them on the path of applying logical thinking to objects, mathematical concepts and every day life in general. Studies have even been shown that kids who are used to comparing and contrasting do better in mathematics later on. I'll talk about the seemingly endless ideas for general sorting in a bit.
Maria Montessori's sensorial work uses "sorting" in specific ways that work to use all of the child's senses, one at a time, in order to refine them. The goal is to train the brain to create more organized thoughts and ways of retrieving information. Montessori also recognized how much children appreciated order in their worlds (a large piece of her main philosophy) and how important it was for them to create this order independently. While the works given to the child are teaching them valuable skills, they don't seem to notice what they're learning. It is delightful work for them. Montessori also believed that when children are given a work that uses senses that they hadn't noticed or are new to the child, the learning and awakening that occurs is just as important. What is learned isn't just kept in isolation with a singular work; the child uses the sensory information and intelligence gained and applies it to other areas of his life, furthering his adaptations and experiences within it. Beautiful!
The categories formed by Maria Montessori for sensorial works are based on thermic sense (detecting differences in temperature), tactile sense (touch), auditory sense (discriminating sounds), olfactory sense (noticing differences between smells), gustatory sense (refining and discriminating taste), baric sense (refining differences between weight or pressure), stereognostic sense (judging shape and size through touch alone), and the visual sense (detecting similarities and differences using the eyes which also develops muscular sense). For a great list of these official works and how to present them, I suggest The Montessori Primary Guide.
While We have some of the more official visual works in our home such as The Pink Tower and (mini) Cylinders, like many other Montessori at home parents, the vast majority of our works have been homemade and Montessori-inspired. While I wish that we were able to have more official work in our home at the moment, I'm happy with what we've come up with so far!
How To Start Sorting
To sort, you child needs at least two different types of objects. A younger child will likely require less categories (sorting by two types) while an older child often can handle three, four or more. Some concepts may be more difficult for a young child while others too simple and uninteresting for an older child. Know where the child is and what they're capable of through observation and of course, trial and error.
Slowly demonstrating each sort for the child before they try it on their own is important. After observing what you've done, the child is free to try on their own. In Montessori, the child's errors are not corrected by adults, though you should observe to see if the sort will need another demonstration next time the activity is done. The child may not immediately catch their errors, but likely will in time, especially if the work is as self-correcting as possible. This helps the child develop decision making skills and confidence. As long as the child seems eager to try and isn't throwing or abusing the materials (a sign that the work is too hard or too easy), let them work. There is much to be learned from noticing and correction your own errors. As hard as it is not to step in and correct (I struggle with this too), much of the value is lost when an adult intervenes.
To mix things up, encourage your child do some of the more tactile works blindfolded. Other sorts can be combined with fine motor work utilizing small object pincer grasp, tongs or tweezers. Your child can put the objects into sorting trays, bowls, cups, egg cartons, divided containers, paper lunch bags or simply line or stack them up. It's suggested, but not necessary, to label each category with a word card. You may discover, especially in the younger child, that your child prefers a certain way of sorting over another. For example my child greatly prefers to sort into some sort of container. Go with what works and attracts your little one!
If you wish to make your sorting more Montessori-inspired, be sure to isolate the one category in which the child is to sort by. For example, if the child is to sort by color, make all of the colored objects the same type of object (i.e. just puffballs, not puffballs, M&M's and marshmallows). Trying to use pleasing objects that are wooden, well-made and in good condition are preferred as a way to attract and entice the child. If possible, try to use something new that the child has never come across before in order to expand upon their experiences. Try to keep the sorting containers identical in size, color and shape.
Ideas For Sorting
First, here are some of the ideas we've implemented in our home so far:
Here are just a small fraction of the many other ways your child can sort:
Deck of cards by black/red
Sort laundry by lights, darks and whites
Garage Sale stickers
Ideas for items to sort by shape:
Shapes cut from cardboard or paper
Ideas for items to sort by size:
Sort towels, dishcloths and washcloths
Cut pipe cleaners or straws (length)
Clothing (baby, child, adult)
Ideas for sorting by temperature:
After a trip to the store, empty the bags and let the child sort by temperature (freezer, fridge, pantry items)
Ideas for sorting by weight:
Fill same size containers with different amounts of liquid
Choose objects from around the home to sort by heavy/light
Ideas for sorting by sound
Fill canisters or jars (contents concealed) with various objects (two of each)
Fill balloons with different sounding objects (two of each)
Ideas for shorting by category:
Pictures of Living and Non-living items
Different types of seeds or grains
Different types of beans, pasta or nuts
Types of plants
Types of stuffed animals (cats, teddy bears etc)
Water, air or land animals
Types of dinosaurs
Sort real or plastic food by food groups
Sort by a few specific numbers or letters
Photos of day and night scenes
Sort playing cards by suit
Types of toys (puzzles, art, blocks, animals)
Sort trail mix contents
Healthy food/junk food
Food we eat with fingers vs silverware
Any kind of stickers
Books (animals, numbers, letters, vehicles)
While I am not a Montessori teacher or professional, all of the information above has been taken from my own reading and researching on the Montessori method. The non-Montessori information comes from my training/education, general knowledge, and experience working with young children.