Originally Posted by HowlerKarma
I also agree that at about 12-13yo is when my DD began to be capable of actually "checking" her work using something besides a basic reality/sanity check.

Along these lines, I've always been explicit when defining "check your work." My definition has been drummed into my kids: "Yeah Mom, I know: it means REDO THE PROBLEM."

IMO, a better phrase would be "Redo your work and compare your answers."

"Check your work" implies that you should go through what you wrote. This is a great way to overlook your mistakes, because it encourages you to replay your original thought processes, and therefore miss your mistakes. Starting from scratch helps avoid that pit.