Longcroft School and Sixth Form in Beverley has been told it requires improvement.
In the latest Ofsted report, inspectors say leaders haven't acted quickly enough to tackle weaker teaching, and pupils don't make consistently strong progress across all subjects.
There were also concerns around the progress of disadvantaged pupils and those with special educational needs and disabilities.
The school say they're working on a plan with East Riding Council to address the areas highlighted for improvement.
Longcroft School headteacher Ian O’Donnell and East Riding of Yorkshire Council said in a joint statement: “We are disappointed that the school has not retained a ‘good’ judgement against the challenging new Ofsted inspection framework.
“However, we are pleased that Ofsted recognises that the new senior leadership structure in the school is beginning to make a positive difference to the progress of all students and offers the potential for rapid improvement.
“It is also pleasing that the inspectors found that students feel safe at school and are confident that staff deal with their concerns.
“ The school is working with the local authority on a post-Ofsted plan to address the areas for improvement that have been identified in their report. We are determined to restore the school to ‘good’ or better as quickly as possible.”