The Helmet Protects the Head
Items needed: two bowl both at least half filled with water; any kind of items such as cut up confetti-like paper, small rocks or pebbles, etc.; a strainer that will not allow any of the previous items through.
seperate your "junk" into two piles that will represent sins we sometimes commit (examples of sin will vary depending on age of students). taking one of the bowl of water you explain that this is like your mind. the water is clear. however when we start to sin and do things God doesnt like it starts to get dirty (add in different "junk" ingredients for each sin). now get out the other bowl of water and explain that we will see this again but this time the mind is shielded by God's helmet of salvation. now as you poor in the "junk" it will not go through to the water because of the strainer. now compare the two "minds" and explain the difference and the importance of salvation in keeping you clean in God's eyes even when you do mess up.
***my children's church class loved this demonstration after i tought the helmet of salvation in our armor of God series and they still remember it to this day!