BingBong, I'm not surprised you wish you'd never started this thread.
You have been criticised for having a thread title that could have AIBU stuck to the front of it, never mind the fact that it is just as easy to stick 'Help me' there, which (amazingly) actually fits with your subsequent post.
This 'mistake' has led to rabid MNs tearing strips off you despite the fact that there has been a steady stream of people saying that they've done exactly what you are going to do, putting lie to:
You can't choose teachers. Unless reasonable requests are granted.
No headteacher in their right mind will agree to any request of this kind, and quite rightly so. So there must be a number of heads in their wrong mind out there then 
It would be unfair and set a dangerous precedent. What IS unfair is a school having a blanket policy that doesn't allow a request to be considered on its merits.
As for dangerous 
Using HolmesSweetHolmes post is just illustrative, all the posts of the same ilk support these ideas, along with the critical underlying ones:
That possibly causing a teacher offence that might last a number of weeks at worst is better than probably causing a child an unnecessarily rough first year.
That 'school' knows best, irrespective of the fact that parents know their children remarkably well too.
That an adults feelings have greater value than a child's needs.
That if parents are given a say in any aspect of school life they will then rule the school.
That parents opinions of teachers are invalid, malicious gossip, although parents labelled 'that' parent are getting their just deserts.
What a load of piffle.
Schools, the last 'great' institutions, where, for some, the concept that the people using their services are customers is so foreign it may as well be from another galaxy (and at least from another service sector).