We've just moved to America for a few years. DD would have been in Y2, but here in the States she'll be in first grade. She'll be going to a private school (does that automatically make it poncey? ). We've worked with the school to do some things that appear to have helped dd (hopefully - we'll know in a few weeks when school starts).
Most of my tips revolve around familiarising dd with the new physical setting, and also doing what we can to ensure she sees a few familiar faces when she goes into the classroom.
The school provided us with the names/contact details of 4 children they thought might 'fit' well with dd, and we've had playdates with two of them (others away on holiday).
We've walked through the building several times, and have seen which classroom will be hers, we've seen the gym and lunchroom and library. We've identified the closest bathrooms to her classroom, and seen the area where her 'peg' will be.
Her teacher wrote all the children a letter, and is meeting with the children new to the school upfront. DD's meeting was a few days ago, and she was able to see the classroom, and where she'll be sitting. The teacher has kindly placed her next to a girl we've met and had playdates with over the summer. DD came out of the meeting very excited.
Interesting to me - all the children in dd's year have an 'orientation' meeting for an hour in advance of the start of school. The children will look around the physical classroom/lower school space while the parents are briefed about practical school matters - pick up and drop off locations, lunch routine, sports, curriculum, etc. The school has thoughtfully scheduled the meeting at lunchtime so that working parents might better be able to attend.
Long-winded (as always!) way of saying - introduce things gradually, and it should be a much easier transition.