I got my copy of Teaching Children Mathematics over the weekend, and I read an article about measurement misconceptions. One of the big misconceptions when kiddos measure with a ruler is what is called tick counting. What that means is that instead of counting the units between the ticks on the ruler, kids count the tick marks instead. It's important that kids have LOTS of practice measuring with nonstandard units to prevent the tick counting error. When they measure using, for example, paper clips, there are no tick marks, so they realize the unit is the length of the paper clip. A line segment is 5 paper clips long. Inch color tiles are a good transition from nonstandard units to a ruler because kids can use both the color tiles and a ruler to measure the length of objects. The measurements should match!
'Broken rulers' are a great way to assess if students really understand how to correctly use a ruler. I made a little freebie that you can use with your kids. Copy the first page (the one with the rulers) on cardstock and cut the rulers apart. You might want to laminate them for repeated use in your classroom. Each student, or pair of students, will only need one of the rulers. The second page has several line segments they can measure with the rulers. I threw in a little problem solving at the bottom of the sheet. After practicing with the broken rulers using the line segments, you could always have the kids do a scavenger hunt in the room (find three things that are about 2 inches long, etc.). Click on the picture to grab yours!
Looking for more measurement practice? Try my Measurement Conversions unit.