Hi, it seems that you have a lot of questions to ask.
The best person to answer all of your questions would be a child clinical psychologist.
In any case, one of the greatest pain in life is (falsely) thinking that we can actually change someone else's mind.
We can first try by befriending them. Try to be in the good books of your child's teacher.
Then you can explain, in various forms and formats and with different people. Some times, our clinical psychologists have to go down to schools to talk to teachers. But even that is not guaranteed success.
Finally, you can despair and give up trying to change someone else's opinion. And pray that with time, the seeds that you planted in their minds will bear fruits and they will understand.
Take care and don't try too hard!