My wife's cousin teaches elementary school, and today several classes at her school are celebrating Pi day.
They are using the date (3.14) to plan fun Pi-related activities. At 1:59 p.m. (3.14159...), everyone is supposed to sing "Happy Pi Day to you!" At some point, the students will run 3.14 kilometers and they will eat pie. My response is that they shouldn't be allowed pie unless they can calculate the area of the pie that their slice accounts for. Maybe that's too advanced. They are only third- and fourth-graders.
Nonetheless, it sounds like a fun day and a great way to teach.