Recently @BiblePlaces has been posting some pictures of winnowing and threshing on Twitter. I realized that one of my old slides was a favorite foto of the practice of winnowing. John the Baptist used this illustration to describe the work of Jesus.
His winnowing fork is in his hand, and he will clear his threshing floor and gather his wheat into the barn, but the chaff he will burn with unquenchable fire.” (Matthew 3:12 ESV)
The Psalmist describes the wicked as being “like chaff that the wind drives away” (Psalm 1:4).
This photo shows a threshing sledge between the adults and the children. While the adults are throwing grain into the air so the chaff can be blown away by the wind the children are enjoying playing in the grain. You can see the effect of the wind on the grain being thrown into the air by the man.
This should make a nice photo for your next lesson mentioning winnowing of grain. Click on the photo for an image sized for PowerPoint.