Have you ever taken a dry dish sponge and dropped it in water? It soaks everything up and gets nice and heavy, full of water! But what if you throw a rock in the water instead? It gets wet on the outside, but stays hard and dry on the inside.
The Bible says we have to "apply our hearts" and learn as much as we can. In other words, when dad, mom, or your teacher are teaching you something cool, you have to switch on "Sponge Mode." You have to open your ears wide and soak up all the wisdom so you end up with a strong, smart head. A kid who doesn't pay attention turns into a rock-head!