Find out what the school's arrangements are for Y7 induction.
As an example, dd1's (state) school organised
(a) individual meeting for parents/child and the head around the middle of the summer term;
(b) new children's induction day some time in early July when the new Y7 could spend the afternoon in school, meet their tutor group and their form teacher and get an idea of the layout
(c) new Y7 and families barbeque on a weekend in July (this was organised by the PTA and was a fundraiser, but also served for the children to meetup in a more informal setting;
(d) Meeting for new parents in the first week of term, where it was laid out to us in no uncertain terms what the school's expectations were (!);
(e) outward bound day out for the new Y7 within the first week or two of the autumn term -- lots of teambuilding type activities;
(f) Informal social meeting for parents, new Y7 and teachers a couple of weeks into term, so you could meet the teachers, as well as your child's new classmates and their parents.
That is more full-on than most schools' induction programmes (the school is v. strong on pastoral care etc and is relatively small) but shows you what can be done to help kids settle in.