To demonstrate how you can compare objects by length, we turn this expectation on it's feet in my kindergarten class by measuring height! How many times have you ordered your class by height just for the fun of it? Have the class do it, by taking two kids and deciding where they go (who goes in front-shorter and who goes in back-taller). Then keep adding kids to the line, letting the rest of the class do an eye-ball comparison of the new line addition's heights. Before you know it, your whole class will be organizing whatever they can get their hands on based on height. Mix it up and switch the line order the next time you do this - tall in front and short in back to help drive this lesson home!