Good work, twelveminus.
However, statistics are statistics and usually need to be looked at carefully. Some comments.
1. Tiffins statistics are not detailed enough to work out exactly about the children coming from Kingston Borough. Not all of KT1, KT3, KT4, KT6 are in Kingston borough. One can safely say that the figure for Kingston would be lower than 31% given above.
KT1 (28 boys)
KT2 (51 boys)
KT3 (114 boys)
KT5 (36 boys)
KT6 (30 boys)
KT9 (11 boys)
The KT1 postcode consists of 777 postcodes.
KT1 4, Hampton Wick, everything t'other side of the bridge, is only 78 postcodes, and is in Richmond-upon-Thames. So out of 28 boys probably only 3 are in Richmond.
Still in spitting distance of the school in any case.
KT3 consists of 770 postcodes these are in:
Beverley ward, Kingston (266)
St James, Kingston (173)
Coombe Vale, Kingston (153)
West Barnes, Merton (96)
Old Malden, Kingston (64)
Norbiton, Kingston (14)
Raynes Park, Merton (4)
So I guess around 10% of the KT3 boys are actually in Merton - around 11 boys.
KT6 consists of
Alexandra, Kingston 18 postcodes
Berrylands, Kingston 32 postcodes
Grove, Kingston 40 postcodes
Norbiton, Kingston 23 postcodes
St Mark's, Kingston 188 postcodes
Surbiton Hill, Kingston 229 postcodes
Tolworth, Kingston 130 postcodes
(660 total in Kingston)
Long Ditton, Elmbridge 90 postcodes
Again, probably about 10% of KT6 boys are not from Kingston borough - 3 boys here.
I didn't include KT4.
KT4 consists of:
Alexandra, Kingston - 4 postcodes
Old Malden, Kingston - 95 postcodes
Auriol, Epsom - 2 postcodes
Cuddlington, Epsom - 108 postcodes
Ewell Court, Epsom - 6 postcodes
Nonsuch, Sutton - 84 postcodes
Worcester Park, Sutton - 232 postcodes
I think the Kingston postodes here are the closest to the school, and the Sutton postcodes are more lilkely to go to Sutton schools. But I just allocated it all to Sutton.
So you could add maybe 4 boys to the Kingston total here.
So not 31%, perhaps, but still 30%.
2. The stats given above are for 2007-2012. Year to year less and less of local children are getting in Tiffins. Situation is getting worse with every passing year and more children from long distances are coming to Tiffins.
I had a look at this.
I took postcodes where the closest part of that postcode is less than 3 miles away.
Figures by year:
new Y7: 69
Not a compelling trend.
And those where the closest part of the postcode is 6+ miles away:
New Y7: 33
And again, not a compelling trend here either. Y11, looks more like an aberration than the start of a trend.
Sorted by distance, these postcodes are all over-represented.
TW7, TW3, TW4, TW5 (Hounslow all 3)
W5, UB1, UB2, UB3 (Ealing)
There are 4 times more boys from TW5 (Heston, Cranford, Osterley) than in TW10 (Ham, Petersham, Richmond Hill).
The UB1, UB2 and UB3 area(s) are the only postcodes over 6 miles in a straight line, minimum, from the school, with more than 10 children at the school. Of other areas of such great distance, usually just 1 or 2 children come from each.
I suggest that the borough of Ealing and/or Hounslow look at building their own grammar school, as clearly many of their brightest children head off to Kingston, damaging the performance of their own boroughs.
3. TGS data also has shown the same trend over the years, with numbers of local children decreasing at much faster rate since 2010.
Trend isn't clear here.