That they are just 1 of 30 and that you don’t get daily feedback like at nursery.
That if they are not a good eater or water drinker they will be really exhausted. Very important that they eat their lunch and drink enough water.
Many are very tired.
Some schools do show and tell and that is the highlight of their week aka showing something.
That settling and making friends is the most important thing and play dates/attending parties can really help with that. All of mine went to the linked preschool so already had friends so settled really easily and are high energy children, however it was much harder for some other children in their classes at the time.
With my first years and years ago the sheer amount of emails the school sent came as a shock. Have a whiteboard type thing to write stuff on for reminders eg dress up days, money required, world book day, bring in a toy, bring in a certificate etc. Share all their achievements outside school too.
Don’t be too worried if you have a child who loses a lot of stuff, they usually get the hang of it eventually. Out of my 4, 2 kept losing stuff for the first couple of years eg water bottles, books, jumpers etc.