Newent Community School and Sixth Form Centre has been placed into special measures by Ofsted.
The news emerged last night following an inspection on January 10.
Letters have been sent out to parents and a meeting will be held with them on Monday.
Headteacher Jane Steele said: "Clearly we are extremely disappointed that the school has been placed in special measures.
"Newent Community School and Sixth Form Centre is a successful school and we do feel very disappointed that the report doesn't acknowledge a lot of our strengths."
A school is placed in special measures when it is found to be failing to educate its pupils adequately.
Ofsted has the power to fire staff and replace the governors and carry out short-notice inspections. If poor performance continues the school may be closed.
The full report has not yet been published online but issues raised in it include pupils of lower ability and with special educational needs not doing well enough and the quality of marking and feedback being inconsistent.
For the full story see tomorrow's Citizen.
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