I agree with you completely. Teachers should do their best to teach their students the right way, and native English speakers should start caring more about their own language and take some time to learn to spell correctly, because bad spelling gives a very bad impression. I'm not a native English speaker and not an English teacher either, so my English is far from perfect, but when I see that so many native speakers can't spell the most common words or don't know the most basic grammar rules, it really annoys me.