I agree with all of the above. We moved to Oz from California when my son was 5 and nearly 6, due to start K in the US and although the school year is quite different here he slotted in just fine. One principal told me that Kindergartens are very fluid. They take a range of children, from those just out of diapers to those already reading and writing. Let me know if your friend needs any more specific school info. The states vary a little, and there are even a couple of American schools here.
Mama to 13, and 10 and 4.