My 6th graders' science textbook had a statement about how if the polar ice cap melted the seas would rise.
To prove to him that was wrong, I had him take a glass of water half-filled and put several ice cubes in and mark the water level.
The next morning he saw that when the ice melted the water level actually was LOWER than before.
He saw for himself that you can't always believe what's preached in government schools.