On the first day of the school have the students make their hand print, fill out an info sheet with the teacher, and measure their height in yarn. Then wrap it up like a time capsule and put a label on it that says "do not open until (the last date of school). Open the time capsule and do the same thing at the end of the year to see how much they have grown and changed.
How to Be That Parent. 10 Simple Ways to Get involved and give back to your child's School this year from No Time for Flashcards