DD started in a crèche when she was 6 months old (we got 18 weeks paid maternity leave in Ireland at the time - now it's 24 weeks). So when she started school, it wasn't such a big step for me.
The main difference was that she was moving on to a learning environment - she'd be learning the three Rs. She wouldn't be babied as much as she was in her crèche and the teacher would expect her to be a bit more independent.
She would also be making new friends although she was friends with a few of the girls already from crèche (and they're still friends now).
In some ways it was pretty much what I expected. I didn't expect the homework to kick in so quickly (second week of Junior Infants 
).
I had to be a little bit more organized on my days off (I worked part-time). No more lazy mornings in my dressing gown. We had to be up and dressed and on time for school. I had to keep an eye on the clock when it got near to collection time. I had to remember which days were P.E. days and put out her tracksuit those days. Her uniform the other days. I had to remember when she needed money for various activities or fundraisers. Or if she needed consent forms signed for various things e.g. school trip. I had to make sure DD put everything back in her schoolbag after she did her homework - pencil case, ruler, copy, worksheet etc. They're a bit scatter brained at that age or maybe that's just DD.
I had to be a bit creative when it came to packed lunches and consider stuff like whether I needed to give her an ice pack in her lunch box on hot sunny September or June days.
I never anticipated so many birthday parties or how much of my disposable income would be spent on kids' birthday presents!
I probably needed more clothes rather than less clothes as she wears her uniform to school and changes into regular clothes after school so she doesn't spill her dinner all down her uniform. I find I've less washing during the holidays as she's only wearing one set of clothes each day.
I've never ironed her uniform. If you hang the items carefully on an airer they dry pretty much crease free. Who irons jumpers anyway?
My biggest tip - please explain to your child that pencil parers should never be used for paring fingers.
Sorry for rambling on a bit. I guess this thread got me thinking back and remembering it all 
. Although it can be a sad time (especially for SAHMs), it's lovely to see them move on in the world and gain in confidence and to see their excitement on 'big' days like the school tour day or sports day etc.