The first year for the Durham exam to have an impact is the current Year 11 doing their GCSE's this year. I know this because I am still in touch with my pupils who were first to do the new exam.
It will be interesting to see how this translates in results. I am not convinced it will make a huge difference. Yes, children used to get in on the back of a huge amount of verbal and non-verbal training who possibly wouldn't get in now but the same children may have been supported hugely by their parents so they did go on to get decent GCSE's. I think the difference, if there is any, will probably be seen at A level.
I also think there is an automatic presumption that the KE schools outrank anywhere else but I don't think this has been the case for a while. I certainly know a friend who taught at Queen Mary's told me about 2 or 3 years ago that they were dancing round the staffroom, having beaten Aston (and Five Ways, I think) in the league tables.
I also believe people underestimate Sutton Girls. Last year we put it 3rd on my daughter's list before Handsworth Girls', and that was based on atmosphere of the school and feedback from children who attend it. If it weren't for distance, it would probably have ranked 2nd. My friend's girl went this year and both the amount and quality of homework given has certainly surpassed my child's at Camp Hill, although it is obviously early days.
At any rate, I would never pick a school based on position in league tables. If a school is in the top 100, then where in the top hundred is neither here nor there. Yes, some of it will be down to quality of teaching at a specific school but more will be down to the quality of the intake and any particular year may be a poor year. I believe, for instance, Handsworth Girls' had a particularly bad year of GCSE results two years ago; this followed one of their best year's ever. Did this mean the school was suddenly going downhill or did it just mean they had a 'right shower' that year as teachers have been known to delicately put it?
Choosing a school is hard. For instance the answer to 'Where could I see my child being happiest?' as opposed to 'Where will my child do the best?' is not always the same.