I realised that the report was on the school website and is downloadable here >>
http://www.hornimanprimary.com/governors.asp
see page 2 and page 8 of the report for more information on this issue
Basically what it says is that a number of the KS2 papers in the writing part of the English assessment were sent back for marking after the teacher assessments and moderation came back with a different score than the official one (that means the teacher assessments and Lewisham's moderation of them did not agree about some children's 'official' level in the writing tests that formed part of the English assessment).
The papers were not regraded, as they rarely are, and so the school is in a position that they are left with a set of results that they and others who have assessed those children don't agree with.
There is nothing the school can do about these assessments, except try and explain the situation, and having been through this in quite some detail as a Governor (as it is our responsibility to do) I can tell you that I am confident that this is not a problem with the school.
As you will see from the report the official KS1 results are excellent. However, unfortunately these are not reported on the various websites that list the school information.
I am happy to answer further questions on this and I know the Headteacher would be happy to talk to any parents or prospective parents about it too.