This is the most basic concept I can teach to very early beginners. Once they know a few good descriptive words I use them to check their progress through other concepts.
Give me the big ball.
If they grab the correct one, I’ll know they understand the concept of give.
Another exercise for big and small is writing. I highly recommend Donna Young’s website. It has every combination of writing paper you could ever need. I often use the larger sizes for my small learners. I’ll write the word in pencil and let them trace over with a fat marker. For my older students, they use more of the college ruled paper.