...is the number of days the kids have been in school. Let me rephrase that. 100 is the number of days school has been open. (None of our kids have perfect attendance. And because of the snow days last week the celebration had to be pushed back two days.) I don't know about the middle school but the elementary school goes all out to celebrate the 100 day mark. Kade's class had a little party and strung 100 Cheerios on a pipe cleaner to make a bird feeder. 100 was used a lot through out the day.