One does need to master the art of correcting though, to keep it nice and pleasant. Then again, some teachers aren't capable of doing it properly
I don't know if any of you have had bad english teachers... but many are really not as good as they should be...
In 4ème and 3ème, I had to do english LV1 because they didn't do german LV1 in my new school. So obviously, being english, the teacher hated me. He was teaching the class vocabulary around planes, and he said "the plane landed down"
I gently (well, I was 12 so it was probably pretty arrogant) explained to him that the correct sentence would be "the plane landed" as "landed down" would be a pleonasm.
So he told me my english was informal, and that his sentence was the formal and correct one (and several classmates made fun of me for this)
Well, I was a bit offended, I speak the Queen's english didn't you know
So I brought a bilingual dictionary in which it stated that "attérir" was "to land" and not "landed down".
Edit : I keep forgetting words in me sentences