Using lego towers, the kids compared heights and widths. Then they had to add or subtract blocks to make their tower the same size as their friends.
Then they practiced measuring them with a ruler. They had to remember to position their tower at the zero mark.
The kids had a sheet for recording their own measurements. They took turns measuring each other (in inches) and recording their results on their pages. This was a lot of fun and the kids were able to compare sizes and discuss.
Next we tried some measuring with a triple beam balance. It always amazes me how quickly kids catch on to using this type of scale. It's also excellent practice for reading numbers and adding two and three digit facts.
We then did a little comparative study. The kids measured out a room using their feet and plotted their findings on a piece of graph paper. Next we held the drawings up side by side and compared the sizes. The purpose of this was to prove that not all feet are the same size and that there has to be a standard of 12".
It was a great introduction to measurement and kids love to play with this tools. It's also a fun idea to just set out the measuring tools (and a clipboard too perhaps) and have them play with them in their own way.