Read everything you can on the school's website beforehand. A lot of them still have videos up from covid, as well as newsletters and blogs. You honestly do need to think about the school for YOUR child - we rejected a fab school for our DD because it just didnt "feel like her". She is so settled and content at the school she ended up at, but it probably wouldnt have been the one I would pick for myself. (She picked a school that is extremely strict because her primary was out of control and she found the learning environment stressful.)
Find out how transition is handled to y7. What is discipline like? how is underachievement or misbehaviour handled?
Do they get a full hour for lunch or just 30 mins?
What would the journey to and from school be like, and consider if the school has a rep for a heavy homework burden
Consider if girls and boys have similar ooportuntiies. Two mixed schools in my area are 65% and 70% boys, because local girls school siphons off the girls. When I asked in Maths, Computer Science, Physics and Chemistry at one mixed school hardly any girls were going forward for A level, and one head of department said that despite huge efforts "girls still saw these as boys subjects" (erm, not at the girls school up the road!).
Is there a flourishing 6th form.
Do they push kids down a certain academic path (if that's what you want) or is it more about being fully-rounded and creative and self-expression.
Ask about choice of options - some schools offer animal care GCSE and BTECs along with A levels. Others offer Latin or German. Many have a "random allocation" of foreign language in y7 so find out if you're concerned they'll be dumped in Spanish and you especially want Frenc. Find out if they do early maths GCSE and if yes is that the only route to do double maths A level. Assess what are the music and arts departments like; what facilities do they have for sports and IT. Do they put on a school play? is there an orchestra or band?
Also look at the library - is it a good space, well-stocked with lots of calm space.
Does the sixth form have it's own common room or block.
Do the kids get their own lockers in Y7.
What extra curricular and school trips are on offer.
Look at the state of the buildings - are there buildings that look very decrepit, as some schools have huge problems raising capital to repair leaking roofs etc.
How long has the HT been in situ, and what vibe do you get.