So, don't ask me why, but my students are required to learn both customary AND metric units of measurement.. at the same time. I understand that it's important to learn them both (especially since Americans are the only silly people to use the messed up Customary system!), but seriously? At the same time? In 4th grade? But anyway, they did pretty well with it. It kind of works because if they master one system, they can use it as a comparison for the other. For example, they really understood ounces, pounds, and tons (well, most of them understood tons... see previous post for the story about the kids that didn't!), so I was able to refer to that when introducing grams and kilograms. Even though there are 28 grams in an ounce, they were able to grasp that both are very tiny units of measure and used for little objects. Similarly, kilograms are comparable to pounds for bigger items.
The lesson was pretty flawless and they were really getting the hang of it. We spent some time discussing the prefix 'kilo' and how it means 1,000. Then, I set them loose on their independent work. I began walking around to check work and almost lost it when I walked over to one student and discovered we needed another talk about 'kilo.' All over his paper was written, "killergrams." Haha. Never a dull moment!