Your anonymous headteacher (“Caught in the exclusion trap”, What keeps me awake at night, 14 December) rather sweepingly says that pupil referral units (PRUs) are not working owing, it seems, to a notion that only 1 per cent of permanently excluded children achieve five A*-C GCSE equivalents.

I do not know how many of the permanently excluded children referred to went to a PRU, how many to a new school and how many were left with nothing. So to link PRUs with all excluded pupils is unfair. In the best PRUs significantly more than 1 per cent of pupils get five A*-C GCSE equivalents. And schools are less likely to exclude a child who is on course to achieve this benchmark, so PRUs do not have a normally distributed cohort.

The best place for any child is in a mainstream school, as long as they are being successful in that school. To keep children in a place that is not working for them is not doing them or the other pupils in the school any favours.

It may be that this school is achieving great things and, if so, that is to be applauded. It may be that the local PRU is one of the few in the country that isn’t doing a good job. But I am tired of seeing statistics brought out to bash PRUs time after time, statistics used with no context and no attempt to understand the full picture. Ofsted does not agree that PRUs are not working (a higher percentage of PRUs than mainstream schools are good or outstanding) and I do not agree either.

Ian Hedley, Head of a PRU in the South West.