Sir - Martin Thomas (Letters, March 9) argues that in response to the city reorganization pupils left city secondary schools to attend Matthew Arnold and Wheatley Park schools to the disadvantage of the former and advantage of the latter. The reality is less straightforward than he suggests.

Entry cohorts at Matthew Arnold since the reorganization have indeed increased (but not at a steady rate and these increases are not solely attributable to pupils who would otherwise have gone to city schools) but at Wheatley Park they have declined.

Entry cohorts for the city schools have, for the most part, increased, remained static or fluctuated around a norm. Looking at pupil performance on the basis of just one year's performance compared with another can lead to unreliable deductions. Trends are more likely to be meaningful. Results for English at KS3, for example (an indicator cited by Martin Thomas), show an overall trend of improvement for city schools from 2002 (while acknowledging a, hopefully temporary, dip in 2006).

Both Matthew Arnold and Wheatley Park were already on an upward trend in relation to this indicator over that period and, in the case of the latter, it is difficult to ascribe this to an influx from the city when the cohort declined.

The Fischer Family Trust Contextualised Value Added (CVA) data (which show how schools are placed compared with similar schools nationally), show improvements in the city schools relative position since reorganization in 2002. In 2006, however, the overall position is much the same as in 2002 but, once again, there is no reason to believe that this is anything other than a temporary 'blip' in an otherwise upward trend.

John Mitchell, Assistant to the director for children, young people and families, Oxfordshire County Council