Ask what are the arrangements for settling in new Y7.
At dd1's school they had the following:
Individual meeting for parents + child with the head, prior to which the child had filled in a form describing their interests, hobbies, favourite subjects etc. Stated purpose was so that we could know who the head was and always feel we could approach her with any concerns;
Half day in early July where all new Y7 went to school to meet their form tutors and the rest of their form group, get familiar with the classroom layout etc;
Sunday afternoon barbeque a couple of days later for new Y7 families organised by the parents association -- there was fund-raising element to it as you had to pay for tickets, but really a way for children to meet up again with their form group in a less formal setting;
Introductory mass for new Y7 and their parents on the first day of school year in September;
Parents-only information evening early in September, where we were left in not doubt as to what was expected of us (!);
Parents, Y7 children and staff social evening about 3 weeks into terms, so we could meet staff and dd1's classmates + parents in an informal setting and start putting names to faces.
This is an exceptional set-up, but shows the lengths that can be gone to. By contrast, the school to which most of dd1's friends have gone to organised individual meetings early in July for the parents + child to meet the head, at which the parents all ended up feeling as if they were being given the third degree. That was it.
Roisin, can you not apply to both the state and private schools and defer decision till nearer the time? You do get a feel for how a school works as you go through the admissions procedure. One other tip is to phone up the school incognito and ask some slightly dozy question about eg. the admissions arrangements. The reactions you get are quite revealing -- some school secretaries bend over backwards to be helpful, others will give you the 'oh god, not another stupid parent wasting my time' routine. Then extrapolate that three years down the line when you have to raise some issue with the school.