Teach Honesty in the Truth and Lie Game. Say something simple like "I have purple hair" and have the kids walk to the side of the line (Truth, or Lie). Fun to let the kids come up with sentences after you've played for a bit.
Great guidance lesson with fun activities! This Activ flipchart for Promethean Board is great for school counselors or teachers teaching a lesson on honesty. It opens with an introductory comic. Then flips to the title page, then the lesson's objectives.