fillie
Just a Mum and by no means an expert - but DD1 started school at a very slow pace and we sort of let it slide during KS1 (finished KS1 SATs on NC L1 - below expected progress). This was primarily because I kept thinking - ah, but she's so young.
We then spent nearly all of Y3 - Y5 seriously doing a lot more at home to help DD1 fill in gaps and master basic 3 Rs skills.
With DD2 (two years younger) - we made a more concerted effort to keep learning ticking away over the summer. Not going overboard - but ensuring that during the summer she was reading, practicing a bit of math and writing (post cards & school assigns a scrap book project about 'What I did last summer' each summer).
I know it can be a drag - an 'Oh, but children deserve a lovely summer' - but it is possible to incorporate a bit of practise on reading/ writing/ arithmetic in a fun way over the summer.
I would genuinely recommend if your DD is struggling - to try a keep a routine over the summer and work on areas where she needs help.
If your school is using Jolly Phonics - their workbooks are a lot like a colouring book - and give lots of letter formation practice as well and 'sounding' out practice. I also think watching alphablocks episodes (www.bbc.co.uk/cbeebies/alphablocks/) with their catchy tunes can be a huge help.
Counting can be done easily - just reading addresses as you walk to the park, counting steps or blue cars. Something simple like looking at odd and even numbers along a street - can help teach counting by twos. Board games like snakes & ladders are great for this - play it backwards to work on subtraction.
Of course baking with Mum/ Dad/ etc... is brilliant for maths - lots of measuring/ timing there.
With reading - although bedtime reading is a lovely time - there's tons to be read around town - billboards, signs, advertisements in trains/ on buses. At the supermarket.
HTH