You might like to ask questions based on DFE performance data:
www.education.gov.uk/schools/performance/
Particularly the average point scores percentage of GCSE only entries against all (including equivalents).
Also Ofsted's Data Dashboard:
dashboard.ofsted.gov.uk/
You may find it interesting to compare schools against the bench marks you think important. Also remember to check the courses entered at GCSE and A Level to ascertain if the academy/school is guilty of any league table manipulation at the expense of attaining pupils full potential.
I think you will find it very interesting.