I would ask a senior teacher about the proportion of low, middle and high achievers and which students they were adding most value to.
I would ask about GCSE options and the numbers which are offered 2 languages or triple science and if there are any other things which are only available to certai X true to and which ones.
If my child getting in is questionable, I would ask for historic info about kids who fit my DC profile in terms of distance etc.
I'd like to know the % going into A Levels and from 6th form into uni and % going onto RG uni.
I might ask about the % playing an instrument or the numbers of Yr7 in a sports team or music group, or the numbers taking DofE at each stage.
If they couldn't tel me any of that stuff (especially the first Q) off the top of their heads, I would want them to find someone who knew or take my details so they could get back to me with answers.
Realise not everyone will be interested in this stuff, but I'm more interested in this than science experiments which are being shown and happen once a year.