Many children at a school rated as "inadequate" have been missing "on average" one day of school a week.
Ofsted inspectors found that teaching at Merchant's Academy in Bristol is "poor" and "pupils cannot read and write as well as they could".
The report, first obtained by the Bristol Post, found a "culture of low expectations" there.
The academy has had a turbulent few years with high staff turnover and a slide in results.
A new head, Samantha Williamson, was appointed in September to turn the academy in the south of the city around.
In a statement, Mrs Williamson acknowledged the result in the Ofsted inspection was "disappointing" but was in line with an internal assessment made by the school.
She said the plan "accurately pinpoints the areas where the academy has been lacking and charts a clear path forward to make rapid and effective improvements".
Colin Skellett, chair of governors, acknowledged that "parents and carers will rightly be concerned".
He blamed the school's decline since the last Ofsted inspection, when it was rated "good", on the poor quality of teaching and an un-engaging curriculum.
At 30%, staff turnover at the school is the highest in the area and has a history of recruiting newly trained teachers.
Mr Skellet said the school has now focussed on recruiting experienced professionals and is fully staffed.
It has also appointed a chief executive principal, Dr Hilary Macauley, and partnered with Colston's Girls' School, which was rated "outstanding" by Ofsted.
Mr Skellet also said attendance was low because a group of pupils were "voting with their feet" by truanting.
"We need to create a school where a pupil can do the very best they can," he said.