DSs school and the attached nursery start the children according to age, starting with the September children and ending up with the Summerborn ones. DS2 is due to start nursery next week, being a "Middle" child.
This means that the eldest children have much more attention fron the staff, simply because there are fewer children in the nursery at the time that they join. By the time the summer born children start at the end of next week, there will be at least 30 children running around playing, demanding attention and, quite possibly, scaring some of the younger ones.
Doesn't it make more sense to start the youngest ones firat and then gradually add in slightly older children? Then they'd have more chance to get used to the nursery and the staff, will have more attention whilst they settle in and then gradually get used to more children as the intak period progresses. Why do they do it the other way round? A week isn't going to make any difference age-wise is it?