Sex offenders hysteria

Unless I've missed it no children have been abused or assaulted as a result of teachers on an offenders list being allowed to work in schools. The hysteria has been created over a perceived risk which no one seems to be able to quantify.
Could there be another agenda here? The government's education policies are already under fire. Enemies both inside and outside of the ranks of labour MPs have a vested interest in dislodging Ruth Kelly the Education Secretary. The new Tory front bench is also in search of it's first government scalp, and Ms Kelly is an obvious target.
While some changes to the way school teachers with a criminal record are vetted and deemed fit to resume their profession may be needed, the current system must be working because up to now there have been no incidents of abuse. To remove Ruth Kelly in the process would be an over reaction and unjust.