You need to become knowledgeable yourself about the details of the alphabetic code and the skill of identifying the various elements of code all-through-printed-words and how to sound out and blend them.
If your ds doesn't know the alphabetic code well enough, he is left with various multi-cueing strategies that, in reality, amount to guessing many words from clues such as the pictures, the context of the sentences, initial letters and 'what would make sense'.
These are all very flawed reading strategies because, in effect, they do only amount to guessing and when the text becomes more difficult, some children are left stranded with no way to improve their reading.
Any good teacher would have tested your ds on how much alphabetic code knowledge he knows to automaticity. So, one question you might ask of school is whether he has been tested in this way and please could you see the test and the test results.
You could also ask exactly which synthetic phonics programme the school is using and which elements of the alphabetic code are they accountable for teaching there. You could ask to see this.
Meanwhile, get very busy tonight doing your homework (if you see this email in time).
I provide very informative alphabetic code charts which are entirely free to download via my free unit 1 webpage along with many other informative resources - all free.
I also provide some assessment material which you can find in a yellow box down the centre column of the homepage of www.phonicsinternational.com . There you will find a range of assessments including some alphabetic code knowledge assessments and some words for blending. If you can manage it, try to get a feel for what your son knows and can or can't do to help him.
If he is an unhappy lad, you could also consider telling him that research is showing teachers some better methods of teaching reading and spelling but that he may not have had the kind of teaching that would help him the most. Of course, I don't know what his school has or hasn't provided so please go careful about what you say with regard to his school - speak in general terms. What I am trying to suggest here is that the pressure can be taken off him and any perceived 'learning difficulties' and some explanation provided that teachers themselves need better understanding of these phonics practices (which is actually the case).
If nothing else, you are probably perfectly capable of helping your son to improve at home if you can find fiftenn minutes or so a night and get into a good routine - so I'm giving you encouragement and hope - do not despair!