THE number of schools classed as poor is likely to increase because of changes earlier this year to the inspection system.
Since the beginning of the year, inspectors have been required to consider whether a school should be labelled as having serious weaknesses if the proportion of satisfactory lessons falls below 87 per cent.
Under the most recent system used to assess schools, inspectors were told to consider this label for schools where 20 per cent or more of lessons were not up to scratch. In 1996 this benchmark was 25 per cent.
Inspection analysts expect that a greater number of primary schools are likely to be identified as having serious weaknesses.
This is because in a small primary, having just one weak teacher could result in the school being marked with one in eight unsatisfactory lessons.
The tougher benchmark is having an impact, according to Brian Oakley-Smith, managing director of Cambridge Education Associates, the largest private company carrying out inspections for the Office for Standards in Education.
"So far, te numbers are so small I would not care to generalise, but ... I think it is intended to have an impact," Mr Oakley-Smith said.
A further hurdle is the requirement that schools must show that a reasonable proportion of their lessons are good, rather than merely satisfactory.
When reaching a judgment on poor schools, inspectors take into account low standards of achievement by pupils and ineffective management, as well as the amount of unsatisfactory teaching.
Some local education authority officers believe that they may have to provide support for a greater number of schools, but that the overall effect will be to raise standards.
Martin Baker, senior adviser for school improvement in Hertfordshire, said:
"OFSTED wants to raise the standards of teaching, but whether that means that more schools will cross the threshold into serious weaknesses remains to be seen."
An OFSTED spokeswoman said that unsatisfactory teaching alone would not mean a school is put into the category of serious weaknesses: "Where the proportion of satisfactory lessons falls below 87 per cent, the inspector will look carefully at all the other evidence."