Learning is fun, the saying goes. But for many kids anticipating another school year, the back-to-school countdown is calculated with dread. Here's a fun and easy-to-do science experiment you can do with your kids that will put their thinking caps on, arouse their curiosity and possibly trigger a positive attitude about the classroom.

Here's how to do "The Wild Card" experiment:You will need water, a glass tumbler with a smooth and even rim, and an index card that is larger than the circumference of the rim.

Stand at the kitchen sink and fill the glass with water. Put the card on the rim of the glass. With one hand, press the card firmly in place while you turn the glass upside down with your other hand. Remove the hand touching the card.

Amazing! The water should remain in the drinking glass. Try the experiment again using more water, then try it using less. Use warm water and cool water and try different size glasses. (Be sure to use a dry index card each time.) The results should be the same. Try to figure out how the experiment works.

How it works: Since there is a larger exposed surface on the bottom of the card than on the top, there is more air pressure pushing up on the bottom of the card than pushing down on the top.Donna Erickson's new book, "More Prime Time Activities with Kids," is now available in bookstores. If you would like to order by mail, please send a check for $12.95 plus $2shipping and handling (total $14.95) to Donna Erickson, P.O. Box 16188, Minneapolis, MN 55416.