Local authority comprehensive schools are the fairest and best ways of educating children.
I have two sons. One went to the local comprehensive, had generally very good teaching and ended up with all As at A-Level and a First and PhD in a science subject.
The second went to the local private school as we thought he would benefit from competition with other motivated pupils. Wrong! The teaching was generally poor and he couldn't wait to leave at 16; his results were OK but not as good as his brother's. After that he went to an unfashionable 6th form college, got all As in 5 A-Levels and a First in a science subject.
And I've seen considerable detail about how schools - especially academies - manipulate their GCSE results to appear more successful than it the case.