Let me share some experiences with you on non-academic aspects:

1. How to count money
2. How to buy food
3. How to be mindful of own properties (even with sticker labels, the items may never come back). Especially when they start to play, they will forget water bottle, wallet, lunchboxes and sometimes even part of their uniforms if they have a few pieces removable, eg pinafore, belt.
4. For all payment made to school, always hand cheques to them instead of cash if they need to hand in to teacher, at least for Term 1.
5. Teach them how to pack their own bag
6. Cultivate habit to inform you automatically of all messages from school
7. How to look out for bullies
8. How to manage the bullies
9. Know where the General Office is is important
10. Don’t buy shoes too big that they cannot run properly during PE
11. Don’t buy the std plastic covers to wrap textbooks, it will fall off or cut them and it certainly does not keep the books in mint condition so it defeats its purpose.
12. Remind that they should try to go everywhere in 2s especially toilets
    1. toilets may not be their size cos it caters from P1-P6 so some of
       the taps not easy to push, a friend around can help, otherwise
       some get out without washing. Yucks!
    2. there may be adults cleaners inside there and nowadays, cleaners
       can be male or female. Going in 2s is safer in case of pedophiles.
13. Caution them that the bookshop is only for buying essentials as I see
    many kids shopping in the bookshop during recess and skip meals to
    buy favourite toys or stationeries.
14. Get an elastic attachment to the wallet to hang on the uniform. At this age, they can lose virtually anything.
15. If the school does not issue a standard notebook, ensure that your child carries one to record all the important dates the teacher wants them to note.
16. If a child has direction problem, advise the child to make a buddy in class to move around until familiar with the school compound as the primary school is at least 10 times the size of a preschool.
17. Lastly, very important to note, remind them not to run but walk in the school compound….too many accidents have happened at the lower primary level and sometimes they lose their milk teeth in this way.

 Edit to add contribution from watmekiasu:

18. how to use the public telephone, esp if child attends CCA in the morning. I was caught

  out twice when CCA was cancelled suddenly

19. get them a wallet with coin compartment. Many of those wallets sold in the nightmarket

  altho nice-looking, have no coin compartment.

20.  I actually find the plastic-covers for books very useful. To prevent it from

  slipping off, cellotape the ends to the book.  

21.  buy a schoolbag in darker colours. Schoolkids are usually made to place (dump is

   more appropriate word if your see them in action) their bags on the floor

  during assembly. The floor is very diry. Bags, socks and shoes become

  stained with black marks easily.

22.  many kids carry similar bags eg SPI, Deutor etc. Differentiate yours with a ribbon,

  tag or something.

23. forget those heavy magnetic pencil cases. Adds a lot of weight to an already heavy

  school bag.

24. If using mechanical pencils (some teachers do not allow for P1’s), make sure

  they have a few ready to use ones. Nothing drives a teacher crazier than a child

  fiddling with one eg clicking repeatedly to get the new lead down etc. If using mechanical

   pencils, buy those that uses 0.7mm lead – less breakage.