Hi there Mrs Spoon - the tricky thing with Jolly Phonics is, it isn't always used 'properly.' It follows a very sepcific philosophy with guaranteed success in 99% of cases, but used inaccurately, it can cause problems.
I don't know how your ds's school are doing it, but I will explain here how it should be done, so at least perhaps you should know what the intention is as far as the scheme and philosophy is.
Following JP, spellings are learnt for each of the 40+ sounds. Words are made from these sounds as they are learnt in groups of 6. In structured, directed work, children should only be expected to independently read words containing these sounds and letters covered.
However, the enabling part of this work is that in spelling, once the children have learnt a sound, they can then spell it, even if it is not the accurate spelling. There are a lot of spellings to learn, and it has to be done in stages. This is great because in the past, when children spent ages only learning sounds connected with single letters of the alphabet, common words like 'night' and 'party' couldn't be spelt properly with any knowlegde at all (unless the children were particularly capable and had spotted the spelling patterns from their wider reading.)
Once the first spellings have all been taught, children can write anything, albeit spelt very basically. However, this results in very important things: a child can communicate in writing anything they want and it can be read, and they are showing they understand and can use the sounds of our spoken words in sequence and choose spellings for them e.g. remember whether one or two letters are needed.
So, at this stage, they might be writing about caicks and things they liek and flouers and their tois, but it can all be read. These spellings should not be corrected, because of course no others are known but will be taught at the right time.
Once spelling alternatives have been taught and the children have the means to choose accurately which ones to use, then some can be corrected as a reminder of which spelling should have been chosen.
So, once the alternative for 'ai' has been taught as 'ay' for the end of words, if a child writes 'plai' then I would say - ooh, remember now, we know another spelling for the 'ai' sound, if the sound's at the end of a word - 'play' has 'ai' at the end, so which spelling would we use?' or something similar - indicating the display which should always be around either on the walls or in a book or on a sheet.
Regardless of the teaching method used, spellings should be corrected when appropriate. For example, if the focus and effort has been on a creative piece of writing, then attention should be paid to that, not on the spelling which may go to pot if all the concentration has been on another focus.It is hard for little ones to get their ideas down, when they have to use their imaginations, remember spellings, remember how to write the letters on the page all at once.
Generally, spellings can only be expected to be correct if the children are taught how to spell, and I don't mean by doing spelling tests. Spelling tests are often a huge memory test and there's a lot to remember with little knowlegde to support it.
If a child hs a consistent problem with spellings that you think they should know, think about how they are actually taught to recall all these sounds and spellings - do they have all the knowlegde and skills to understand why these spoken words are represented as so on the page?
Haven't got time to preview and check - any spelling errors are typos, honest!!