An academy trust has not taken effective action to address failings at a secondary school, the education watchdog has found.
Carleton Community High School in Pontefract has been rated as "Inadequate” overall by Ofsted.
Inspectors have now placed the school in special measures and criticised leaders, teaching and Pontefract Academies Trust, which runs the school, for failing to make improvements.
After converting to an academy, Ofsted’s previous inspection in 2015 found the school required improvement across the board.
The latest inspection report, published on Thursday, said: “Many of the weaknesses identified in the previous inspection report remain. Leaders and governors have not moved promptly and effectively enough to resolve them.”
The academy trust said it is disputing the "Inadequate" rating, and a complaint and review process is underway with Ofsted.
Inspectors said in the new report that governance was not rigorous enough, and that leaders were “overgenerous” in their assessments of how well the academy was performing.
Ofsted recognised that the academy trust had commissioned a “Review of Governance” last year and the school’s governing body will now cease to operate in its current form from Friday.
But the education watchdog said the action “has not been timely enough to reduce the weaknesses of the school.”
The report said: "Governance is weak. Governors have not held leaders to account rigorously enough to bring about sustained improvement.
"Leaders’ assessments of how well the school is doing are overgenerous. Leaders are not rigorously checking and then promptly acting to eradicate the variability in the quality of teaching at the school."
The school is among eight that are part of the Pontefract Academies Trust including The King’s School in Pontefract, one of the oldest schools in Yorkshire founded as a grammar school in 1548 by King Edward VI.
Carleton Community High School was rated as "Inadequate" for its effectiveness of leadership and management in the latest report.
Ofsted judged the school to be "Requires Improvement" for the remaining three categories: quality of teaching, learning and assessment, personal development, behaviour and welfare and outcome for pupils.
Julie Craig, chief executive of Pontefract Academies Trust, said: "Whilst we don’t believe that the grading that the inspectors have applied is accurate, we do accept the recommendations within the report.
"In fact those areas had already been identified and feature significantly in the in the 2016-17 School Improvement Plan.
"To satisfy the requirements of the inspection outcome, we will need to adjust some of the actions and accelerate the pace and impact of our work. That process is already underway.
"We are proud of the improvements we have made at the school and, for that reason, we have disputed the grading.
"The complaint and review process is still in progress, but none of that changes our intentions to implement the plans that we believe will not only improve the grading at the next inspection but, more importantly, will continue to improve the school for the benefit of our students."
Ofsted praised the school for its safeguarding and recording systems, preparing pupils for life in modern Britain and making them feel safe.
It will now be monitored by Ofsted following the "Inadequate" rating, and further inspections will take place in the future.
Visit www.reports.ofsted.gov.uk to see the latest inspection report in full.