I've seen many variations of this activity. The first time I did it, we used peanuts (in their shells). Most schools would probably prefer you avoid peanuts, which is easy enough to do. I've also done it with apples, pond stones (you can buy a bag of polished ones in a craft store), shells, etc. Regardless of what you use, the procedure is the same...
You're the proud parent of a newborn pond stone. Take your newborn and fill out a "birth certificate" - provide measurements and a detailed descriptions, as well as a birth picture.
Your stone is now 2 years old and interested in playing with the other stones in your neighborhood. Mix up all the toddler stones at your table and try to find yours.
Your stone is now 4 years old and headed to preschool. Gather all the stones from 3 neighborhoods (lab tables) together at a central preschool. Again, mix them up and try to find yours.
Time to head to kindergarten! Everyone in the class will bring their stone to the kindergarten. Additionally, some stones from another town are bussed in, so they will be added to the mix. Mix all the stones together and try to find yours, one last time.
Some questions to consider:
-When was it easiest to find your stone?
-When was it the hardest?
-How were you able to identify your stone?
(These questions work better for apples, shells, and peanuts):
-What is a variation?
-What were some variations you noticed in the stones?
A variation on the activity:
After students have identified their stone within the groups, have them exchange descriptions with another student. Can that student find their stone? Can they kind the other student's stone?
A good lesson in providing thorough descriptions and complete information.