As part of our plant unit we planted rye grass seeds. The students watched as the "hair" grew and grew. We measured how tall our hair grew, charted it and compared who in the class had the longest grass hair. Then the students gave their person a hair cut. We remeasured and compared our results again.
If you would like to do this activity with your class, you can find directions and materials at my Teacher's Notebook Store. - Thanks:)