I am afraid that teachers are often in the same situation as I am when my car breaks down. It works fine and I can drive it. But the moment something goes wrong I am helpless and have to call in the experts. In the case of spelling difficulties, experts are seldom available and those who are available are not always particularly expert.
Most children do learn to spell because they notice words and get interested in them and want to get them right and this would happen whatever the teachers did. But few teachers understand how the spelling system works, nor how the child's mind is working when they learn it. So, like me with my car, they can't put it right. I am afraid an awful lot of time is wasted in most schools on spelling lessons which are hopelessly ineffective.
One cause of trouble is that adults who can already read and write experience things very differently from young children who are just beginning. Once we know how a word looks we pay little attention to how it sounds and we think we hear the sounds which are supposed to be made by the letters we can see. But children who have not yet seen the word and can only hear it may experience something very different.
For instance we think we can hear the p in spin, because we have seen it again and again and know that that is how it is spelled. But to many children, who have never seen the word and are trying to work out how to write it, that p sounds like a b. There are huge numbers of other words with other spelling patterns, where an adult's perceptions of the sounds, because s/he is already a competent reader and speller, are quite different from those of the child, who is beginning to learn. This problem develops beyond the mere misspelling of the words. The children realise that they are not hearing what the teacher expects them to. That creates confusion in the children, anxiety in the teacher and, worse, a lowering of confidence all round in the children's ability and in the spelling system.
Another difficulty for teachers is that children learn to spell in stages and we need to be able to recognise these and know the sequence of them if we are to teach effectively. Some misspellings, which would be a worry if they came from a child of eight are a sign of normal progress in a child of six or seven. This can cause teachers to become alarmed and see problems where there are none and also sometimes to overlook real problems.
It is not the teachers' fault. They have little training in teaching reading and almost none for spelling, which has been a topic almost totally ignored for decades by teacher trainers and by educational research. Such training as they have received is based on faulty research. A great many teachers feel frustrated and discontented about this, knowing well they should be doing better. However, some people are working on it now and it is possible to get hold of the facts about spelling and wise advice for teaching it - that is, of course, if we know where to look and are resourceful and determined!