In St Sampson's High school's latest Ofsted inspection, it rates 'good' in every category, after a 'disappointing' report 2 years ago.
The inspection framework covers quality of education, behaviour and attitudes, personal development and welfare, and leadership and management.
Each category is graded either Outstanding, Good, Needs Improvement or Inadequate.
In 2022, the Guernsey secondary school scored inadequate in three out of four areas - Ofsted said it was 'not good enough.'
Inspectors returned this year on 19 and 20 June.
They praised the new curriculum and its ambitions for all pupils, and found high expectations around pupil behaviour and clear routines.
Literacy is also improving and there are a range of after school activities.
Inspectors, however, did find that subject leadership amongst teachers needed to improve.
The director of education Nick Hynes has been congratulating headteacher Vicki Godley.
"When Ofsted inspected St Sampson’s High two years ago, the outcome was disappointing for everyone connected with the school.
During the last two years Vicky and her team have worked tirelessly to improve the school, acting swiftly on the areas that were identified and the judgements of this re-inspection are testament of that hard work.
We said two years ago that we recognised there needed to be a change in culture at the school and that this doesn’t happen overnight.
Vicky, her staff, students and parents should be incredibly proud of the steps they have taken together in the last two years."
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