Stop Lying!!!

So we have been struggling lately with Tanner and Boston lying to us. It is so frustrating when you know they are lying and they just stand there and tell you they didn't do it when you know they did. Boston mostly Lie's about making a mess and just blame's it on Tanner. Tanner on the other hand comes up with these elaborate stories to cover up what he has done wrong.

 I am having the hardest time getting through to them that it is wrong to lie even if it is a little lie and that you are in more trouble for lying than your are for what you have actually done. 

So if anyone has any suggestion's they would be greatly appreciated.