Well I've enjoyed reading this thread, even if a lot of the ideas about what a teacher should say are ill-informed nonsense. A poster ages ago mentioned 'lies to children' - well I was until recently a science teacher and I taught that water boils at 100'C, which most of you will believe. I chose not to say that water boils at the point at which the combined total vapour pressures within the mixture reaches the local vapour pressure. I did not dream of discussing homogenous and heterogenous bubble nucleation and when these could be regarded as sufficiently rapid for the liquid to be considered to be boiling, nor whether the water was in a multi phase state, nor any of the things that are necessary for an even basic understanding of the changes of state and heat transfers taking place. They all understood how to make a £$%^& cup of tea though and learnt quite a lot (I believe) about the states of matter needed for GCSE science. I don't think that made me a bad teacher (although a refusal to be seduced by a three part lesson apparently did) and my students both enjoyed classes and learnt what they needed to move onto more advanced lessons.

The question raised in the OP is whether a teacher who explained the work in this way, through limited knowledge or through simplification, is a bad teacher,

Well - as a traditional musician whose main instrument is the highland bagpipes, I am pleased to inform you that there are only nine notes, which is sufficient to play all music of worth and two of those are traditionally given the same name (in the canntaireachd). So there. There are no sharps and flats and there are a sufficiency of notes within those nine to cover some major and minor scales. And the range of the human voice too, except you can't hear anyone over the sound of the pipes. At least pipes play in tune, rather than the horrible compromises accepted by many other musicians...

My second instrument is the fiddle (and all classical musicians play the fiddle, they just had an Italian teacher somewhere in their past). I must admit I've been quite impressed to hear that everyone has agreed that B sharp exists. Amongst classical musicians I had thought that was anathema since equal temperament took over orchestral music sometime before I was born. I have always understood that before ET all keys had different flavours and that to be in tune, and to form pleasant harmonies, some subtle variations to the playing of notes was needed. Fortunately (well unfortunately for this argument, but fortunately because some of the players are nice people and fun to play with) when I play with fixed tuning instruments (box players) I have to play the same notes as them or sound out of tune. Admittedly when I play with fiddle players who play Swedish music and strive to play in tune with their wonderful harmonies I do not always succeed, but that is the result of my poor standards, which is not relevant to the discussion.

In the music that I play, unless I am seeking harmonies, B sharp is the same as C on any fixed tuning instrument. Anybody who plays by ear on a non-fixed tuning instrument they will vary the pitch to be in tune with other instruments whatever you call the note. Anyone who plays on a fixed tuning instrument cannot.

Someone said that there is a difference on a guitar. I'm not a guitarist, but I think not. The best guitarists I know concede that they cannot play 100% 'in tune'. Is there a difference between Bsharp and C on a guitar ? Ask a guitarist.
Any bagpipe teacher will tell you that there is no B sharp. Or any sharp or flat for that matter. That doesn't make them a bad teacher, just that they teach bagpipes.

As I said, I enjoyed the thread and this is my first proper post here, but it does seem to be knocking straw dollies. Enharmonic notes exist in non-ET music because the world is not perfect, but most players working in one genre will never have to worry about it. And even if they worry, if they play by ear they will accommodate or ignore it. The theory will not make a blind bit of differenece.

I expect that guitar teacher is doing a grand job if after three years your child is still enjoying playing and progressing.

Thanks for your time. (Did you really read all this ?)

Greg in London