Hi IWereAbsolutelyFuming
I think you may mean me, as previously posted somewhere on here I am a parent Governor at Horniman School, and can confirm that we have been looking very closely at these KS2 results.
I will need to dig out the paperwork but a good place to start would be the 'Governors Report to Parents' from September/October 2011 which went out to all parents last term. This included these results and an assessment of the reasons behind this 'dip'.
When I get a chance I will dig it out and post a summary.
Please feel free to PM me if you have any questions in the meantime.