Many lessons expect upper elementary students to measure the diameter and circumference of a circle and discover pi. I find that upper elementary students do not measure accurately enough to do this. I have reversed the order of this lesson.
I use the page shown above to introduce pi. Next, I give them a variety of round plastic lids to measure to the nearest millimeter. I have them record their measurements and see how accurately they measured based on the ratio.
To download Pie for Pi Day, please visit this post at Artistry of Education.