No! Don't teach your sons any more spelling skills than is absolutely necessary! A literate person on the internet has only two choices: correct other people's mistakes and be branded a Grammar Nazi, thereby attracting more vitriolic responses than actual Nazis, or let it go and quietly wonder why you learned to spell in the first place. Ignorance is bliss.

By the way, when I type "theif", a little red dotted line appears under it. Am I the only one who gets this?