The number of private schools judged good or outstanding by Ofsted has dropped for the first time since 2011, data published today reveals.

Figures from the inspectorate show that 76 per cent of all private schools’ most recent inspections in March 2015 were good or outstanding, representing a drop from 77 per cent up to August 2014.

The proportion of schools judged inadequate has also risen, from 4 per cent in August 2014 to 6 per cent in March. A report published by the watchdog today said this was partly because of higher standards introduced by the Department for Education in September 2014.

A new judgement category on schools’ early-years provision, introduced in September 2014, has also brought down ratings. Today’s report said more than a quarter of the 46 schools for which an early-years judgement was made were found to be inadequate.

The figures cover almost 1,000 of England’s 2,400 independent schools. Ofsted only inspects “non-association” independent schools, which do not belong to independent school associations such as the Headmasters’ and Headmistresses’ Conference and the Girls’ School Association.

Many high-performing independent schools are members of these associations and are inspected by separate bodies, including the Independent Schools Inspectorate.

Ofsted’s report warned that a growing number of schools were failing to meet “independent school standards”, which are set by the Department for Education and include the quality of education, pupils’ spiritual, moral and cultural development, pupils’ health, welfare and safety and the suitability of staff and premises.  

The proportion meeting all standards fell from 79 per cent in August 2014 to 74 per cent in March 2015, it said.

It said London had the highest proportion of outstanding independent schools, but it also had the highest proportion judged inadequate, at 9 per cent.

The latest Ofsted figures on state schools reveal that the number judged good or outstanding is at a record high of 82 per cent.