Based on my dd's own experience of Y7 and that of colleagues/friends (using a range of schools), you will also need to consider the amount/management of homework they receive.
My dd received lots of homework in Y7 and it used to take her far more than the 90 minutes that the school said we should allow for. This was for a number of reasons - some subjects were new to her and some were much harder - also some involved lengthy practical tasks. Often teachers required the homework to be done by the next day. I found that it took about a year for her to manage all of this - it is a skill that they need to learn themselves.
Any arrangements that you put in place will need to allow for this. For example, if you used a childminder outside your home, there would need to be space for your child to start there homework, as it would be too late by the time she got home.
I think that if I was in your position, I might see if I could find a gap year student to come to your home after school, see if I could negotiate to leave work earlier on a couple of days a week and encourage a couple of visits to the school library after school on other days.
As others have said, children change rapidly during Y7 and I think that even if you put some of these arrangements in place, the need might reduce by Y8. However if you have younger children, they will also have the same concerns when they go into Y7, so perhaps an after school nanny is the answer.