Hi rosyposyandc
First the report has said that some of the time 'he gets it' - whatever it is they're recording (writing his name, tying his shoes, writing numbers the correct way, etc...).
He won't be alone. A lot of children will start Year R without any formal education at all.
I just want to warn you that Class R is a kind of weird (but wonderful) experience. There will be DCs who come already able to read and it will feel like they're reading 'War and Peace' while you're son is struggling with 'See Spot'.
My advice is focus on where he's at and remember that he's an individual and has his own strengths, which he and his teachers will discover. It's very important that you're positive and show him you have confidence in him. It's a silly thing, but if Mum's in your corner as a kid you really can conquer the universe.
For Class R the 'big things' seem to be counting (to 10, then 20, and then 100) and reading (moving from being read to by someone to gradually decoding words for yourself). This isn't an instant process. It's gradual, sometimes with what appears to be instant leaps. And it can be a real struggle - you just have to keep plugging away at it (presuming there are no learning disabilities of course).
What you can do are play simple counting games (snakes and ladders, counting candies, counting food on your plate, etc...) and read, read, read to him. Make a real point with reading of showing him where you're at on the page.
I'm not sure where your DS is at with writing - but try not to worry too much about him knowing letter names (a, b, c,) since these days the schools really focus on letter sounds as part of teaching reading phonetically. If he likes writing (letters or numbers) invest in some chalk and let him decorate your patio or the pavement in front of your house.
Finally remember this is a marathon not a sprint. There will be good steady patches of progress and there will be points where it's all struggle. Keep a routine, try and go to workshops/ reading mornings/ maths games days/ etc... at the school, when you can - but most of all keep good lines of communication with his teachers and keep asking for advice on what you can do at home to support learning.
For age 4 - I'd recommend a few things:
alphablocks: www.bbc.co.uk/cbeebies/alphablocks/
jolly phonics books help with the sounds letters make in English - workbooks available a most good newsagents/ book shops.
Numtums - early years counting games: www.bbc.co.uk/cbeebies/numtums/
BBC schools early learning page has a lot more: www.bbc.co.uk/schools/websites/eyfs/
Learning is an exciting process for your DS and to be honest for you as well - you'll be so thrilled when he 'gets it' - it really is 'taking first step' big when they can read their first word, their first sentence, etc...
I've been surprised at how much support I've had to provide (much more than when I was at school back when dinosaurs roamed the earth) but I've loved the time with my children and really enjoyed helping their learning along.
HTH