But these examples have completely different meanings and if someone graduates from grade school without knowing how to use a contraction, that school failed. The fact that people can't be bothered to check their spelling when they have doubts about a word makes me wonder, sometimes. I actually saw someone write "I have know idea..."- how the hell could they not know the old way of scolding kids "N-O means no!"?

This is third grade stuff.

OTOH, a friend told me that when he was in school, a teacher said "For those of you who are good at spelling, kiss that goodbye because after four years here, you won't be able to spell worth a crap".