Yes, this is true; an interesting question is how to teach your students this through your own failures and still get through the curriculum on time ;)
Well Tom,
I've told my children,(my own, I'm not a teacher), That its OK to make mistakes, that's how we learn what doesn't work.
Besides: "The only mistakes that we don't learn from are the ones that kill you"
AND! " Never take advice from a man who is missing some fingers!"
If the teacher can hoselty say they did all they could for the child to help them learn, they cannot blame themselves if the child still chooses not to succeed.