The head of Caister High School - where 'standards have steadily declined' according to Ofsted - said steps are already being taken to turn its fortunes around.
In an Ofsted report published on Wednesday, inspectors graded the arts specialist secondary as 'inadequate', downgrading it from 'good'.
The inspectors, who visited the Windsor Road school last month, said the quality of teaching, behaviour and safety of pupils and leadership 'required improvement' and the achievement of pupils was 'inadequate' - the lowest grading they can give.
Despite damning criticism in the report, headteacher George Denby said the school - which is poised to become an academy - remained positive.
He said the move to academy status coupled with Ofsted's recognition that improvement measures had already been put in place, saved Caister from slipping into special measures.
'The report didn't tell us anything we didn't know, that's why we already had measures in place,' said Mr Denby.
'It's based on previous attainment and that has been an issue for a lot of schools; we saw Lynn Grove crash from outstanding to inadequate. It can happen to anyone, anytime.'
The report said teachers' expectations of students had not been high enough, that attendance was inconsistent, and there are missed opportunities to produce longer pieces of written work in class.
Mr Denby said action was taken after changes to GCSE grading saw results dip last year, and a raft of 'new initiatives' were introduced last September.
'Straight away we put in place a number of new initiatives with a focus on raising standards,' he said.
'One, for example, is using impact learning which is a professional developlemt course for teachers that focuses on positive instructional language.
'We look at specific language and make sure we're using it and make sure we're giving positive instructions to pupils.
'That has been in place for almost a year now and it's making a difference.'
While stating the leadership and management of Caister required improvement, Ofsted's inspectorate team acknowledged the staff's ambitions and said: 'The disappointing GCSE examination results in 2013 gave them a renewed sense of purpose and triggered an immediate, proactive response. Systems for monitoring, evaluating and reviewing the work of the school were redefined.'
Mr Denby, who has been at the Caister school since 1990, declined to reveal who the school's new academy sponsor would be, but said it was likely to be revealed next week.
He said: 'I think the sponsors we've chosen are innovative; they have some good ideas but it's still possible for the school to retain autonomy.'
'We pushed to work with them because of the way they operate. I've been to see their schools and I've been really impressed.'
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