But the range of secondary selection exams used in the authority was criticised as unfair in the report from the Office for Standards in Education.

Kent’s failure to support children with special needs effectively was also highlighted by the inspectors, as was the patchy quality of its services across the county.

The report identified signs of “continuing improvement” by the Conservative-run authority and said its work was effective in three-quarters of schools.

Kent is a comparatively affluent county and has examination results above the national average. But it also has one of the most confusing education structures in Britain, with almost every type of school represented in the single authority.

Inspectors praised the quality of senior management and the way it was dealing with a “difficult legacy”. Headteacher appraisal, governor support and consultation arrangements with schools were also commended.

However, the report found, “Considerable variation between the performance of schools. There are some very good and some very poor schools in the LEA compared to national standards.”

Alongside criticism of inconsistencies and delays in selection at 11-plus, this is likely to fuel the debate over the future of Kent’s 33 grammar schools. Campaigners are expected to push for a ballot on the issue later this year.

Policy on special educational needs is also criticised. “The LEA has not adequately costed or resourced its policy for inclusion. Pupils with SEN and their parents are not consistently well served,” the report says.

It calls for improved monitoring of resources and the eradication of delays in the statementing process.

Kent education chair Paul Carter said the report vindicated its efforts to “streamline” the 11-plus.