Pupil-teacher ratios figures are not available by key stage because the teacher numbers from which they are derived are collected by phase of education only. Figures by phase of education are available through the following links for each local authority in England back to January 1998:
January 1998 (Table 7a)
http://www.dcsf.gov.uk/rsgateway/DB/VOL/v000130/index.shtml
January 1999 (Table 7a)
http://www.dcsf.gov.uk/rsgateway/DB/VOL/v000109/index.shtml
January 2000 (Table 7a)
http://www.dcsf.gov.uk/rsgateway/DB/VOL/v000192/index.shtml
January 2001 (Table 7a)
http://www.dcsf.gov.uk/rsgateway/DBA/VOL/v000288/index.shtml
January 2002 (Table 7a)
http://www.dcsf.gov.uk/rsgateway/DB/VOL/v000359/index.shtml
January 2003 (Table 7a)
http://www.dcsf.gov.uk/rsgateway/DB/VOL/v000417/index.shtml
January 2004 (Table 7a)
http://www.dcsf.gov.uk/rsgateway/DB/VOL/v000495/index.shtml
January 2005 (Table 21)
http://www.dcsf.gov.uk/rsgateway/DB/SFR/s000603/index.shtml
January 2006 (Table 25)
http://www.dcsf.gov.uk/rsgateway/DB/SFR/s000603/index.shtml
January 2007 (Table 25)
http://www.dcsf.gov.uk/rsgateway/DB/SFR/s000743/index.shtml
January 2008 (Table 27)
http://www.dcsf.gov.uk/rsgateway/DB/SFR/s000743/index.shtml
The available information could be provided only at disproportionate cost.