Let's take a look at a couple more examples of word sorting so you can be sure your child is on the right track. The first example would be a student who is looking at the difference between short vowel pattersn
Here is a cute clip that shows how a student can explain their thinking and sorting. This should be part of the homework when sorting - talking about why the words belong in the various categories.
There are lots more videos out there but wouldn't it be fun to make your own and share it with us?