I attended a conference where Kathy Hall was speaking about synthetic phonics at around the same time that the article ZepherineDrouhin posted was written. It was very clear that she had very little understanding of the English alphabetic code, or SP teaching, 'works'. Which is not surprising as she has spent a long academic career promoting 'whole word'/'look and say' methods of teaching reading.
It is an indisputable fact that the written word evolved by the 'encoding' of the sounds in the word by means of alphabet letters. The problem with the English language is that it is made up of words from a huge number of other languages which remain encoded as in the originating language. As no two languages use the alphabet in exactly the same way to encode sounds we have ended up with a code which is complex and needs to be taught in a very structured, systematic way.
As far as spelling is concerned, in the initial stages of learning to read and spell children do not have all the code available to them, but, once the 44ish 'sounds', plus one way to encode them, have been taught, children have the tools with which to make a plausible (i.e phonetic) spelling of any word they want to write. Once the more complex code (i.e the different ways of spelling sounds) is introduced a good SP teacher will do lots of word level spelling work in which children will be sorting words according to the way the target 'sound' is spelled, looking for spelling choice probabilities (there aren't any reliable 'spelling rules')and learning word specific spellings.
The very fact that children have to look closely at words in order to work out what they 'say' encourages a habit of paying close attention to the detail of the letter use in the word and makes them more likely to remember the specific way that sounds are spelled in words. Most children who have been taught the whole 'code', with equal emphasis placed on spelling and reading, will have no problem with spelling. Early phonetic spelling will be replaced by 'correct' spelling as they are taught it. A few will never really master it, but their phonetic attempts are at least readable, which is more than can be said for the children who have never been properly taught the connection between letters and sounds and who think that spelling is a matter of hurling a dimly remembered 'letter string' onto the page and hoping that they've got the right letters in the right order! I work in KS3, remediating reading and spelling, and I see a great many of these...
It is really helpful to be very clear that every sound in every word is represented by a piece of 'code', however bizarre that code may seem to those who believe that some words are 'not decodable'. What they really mean is that they don't quite understand how the code works. I think that 'one' and 'two' are probably the oddest words that children will encounter early on (forget about 'Cholmondley' pronounced 'Chummly', that's for adults) Not really a hugely difficult pair to come to terms with...