Inspectors found Wennington Hall School to have inadequate leadership and management and quality of teaching, learning and assessment.
Personal development, behaviour and welfare requires improvement, while outcomes for pupils were also rated as inadequate.
However, inspectors said that new headteacher Marc Peart has accurately identified the school’s weaknesses and gained the support of staff.
Leaders have already taken some effective action to secure improvements.
The head of care has taken urgent action to improve the quality of residential provision.
Residential pupils are well cared for, happy and safe.
Safeguarding is effective. Leaders have ensured that robust systems and procedures are in place so that pupils feel safe.
Most pupils attend school every day and on time.
Pupils’ behaviour has improved and the number of exclusions has decreased considerably.
The school, which can support 80 boys aged between 11 and 16 years old, currently has 64 pupils on roll, of which 14 are boarders.
All pupils are identified as having social, emotional and mental health needs and have an education, health and care plan.
Until this year, frequent changes of leadership, uncertainty about the school’s future and financial concerns took leaders’ attention away from improving the standard of education, and staff morale has been low.
Despite some recent improvement, teaching is inadequate.
Teachers’ expectations are too low, their subject knowledge is weak and time in lessons is not used well.
Teaching does not enable pupils to become resilient and perseverant learners.
The school does not meet all the national minimum standards for residential special schools.
Ineffective curriculum planning exacerbates weaknesses in teaching and learning, including in English and mathematics.
Pupils do not perform well at the end of key stage 4, and are not sufficiently well prepared for their next steps.
Leaders’ strategies to support the achievement of disadvantaged pupils and those pupils with special educational needs and/or disabilities (SEND) are not based on a clear understanding of the barriers that these pupils face.
Assessment is weak, and teachers do not know or understand how to assess pupils’ learning in their subjects.
As a result, neither leaders nor teachers have the essential information they need to evaluate pupils’ performance.
As reported in the Lancaster Guardian in March 2017, the school was previously rated inadequate.
As a result of whistleblowing concerns about standards of care at the school, an investigation was commissioned by Lancashire County Council to assess the safety of pupils.
There have been four interim headteachers since the previous inspection.
Following the previous inspection, the Department for Education issued the school with a directive academy order, but a suitable sponsor has not been found.