As schools are preparing for the second round of inspection, the NAHT has canvassed the views of 1,220 heads who have undergone the process in this academic year.
They complain that inspectors' reports to heads are riddled with errors. Almost a quarter of the heads in the survey said that grades awarded to teachers were for lessons they had not taught. Others said grades given to heads were different from those that teachers had been given in their interviews with inspectors.
Around 40 per cent said there was increase in staff illness in the two to three months after the inspection. Almost three-quarters reported increased disaffection and lack of motivation. Of these 90 per cent attributed the effect to the inspection.
Few considered inspections provided value for money in terms of identifying areas for improvement. Most said the issues identified by inspectors were already in the school development plan.