It is a million years since I was in secondary school (left in 1984). Dh is a bit younger but not much. Dd is an only and her cousins all in their 20s now and not in our area. What do I look for? What do I ask? One of the schools (we are just outside the area but looking anyway) is an all girls former grammar- top in the county area. The others are mixed comps. Oh wise and experienced parents of secondary school students, apart from "the feel of the place" what should I be on the look out for. Dd is very academically able if that is an extra factor you can tell me about.
If she's academically able then ask when they are put into sets, especially for maths. The new GCSEs haven't come in properly yet so things will change but ask about what is offered for the most able - triple science, further/additional maths, maths challenges, two MFL etc. What about extra curricular offerings?
If you're interested in results, go to www.compare-school-performance.service.gov.uk and dig down into performance by prior attainment at KS2 so you can see exactly how well their most able students are performing, and indeed how many able students they have.