TEACHERS at crisis-hit Addington High harm their students' English because they struggle with grammar and punctuation themselves, according to an official report.
Ofsted inspectors who visited the school in December have said the school is not ready to leave the special measures imposed by their colleagues in October.
In a wide-ranging report, lead inspector Christine Raeside said: "In some lessons, teachers or teaching assistants reinforce mistakes in writing because their own skills are not secure.
"The school action plan acknowledges the need to improve the expertise and confidence of staff in this area."
Chairman of governors Jo Tanner acknowledged work needs to be done to promote "high levels of literacy and understanding of grammar" among teachers.
She said: "It is something that we are working on as the governing body to tackle, we are looking at ways to support our teaching staff."
She said that she did not believe the problem of poor grammar was exclusive to Addington High nor to teachers.
The report comes as the school is set to become an academy in April, sponsored by Bromley school Ravens Wood, in a bid to improve.
The two schools have already been working together, particularly closely with Ravens Wood's former vice principal John Hernandez.
Ms Tanner rejected any suggestion that the latest poor report – which praised leaders' commitment but said progress has not been fast nor consistent enough – was a sign of things to come with the partnership.
She added: "As governors we are disappointed with the outcome of the latest inspection report.
"But what we are pleased to see is the acknowledgement of the initiatives we have put in place and that they are acknowledged to be the right ones to take the school forward.
"I think Addington High has its challenges and the pace of change expected under the new Ofsted framework was always going to be challenging.
"Our goal remains the same: to make sure that children who leave here do so with the best education they can receive."
The report looks at a range of measures including teaching, academic achievement and students' behaviour.
Forty-five per cent of students achieved the benchmark of five good GCSEs including maths and English in 2012, an improvement on the year before.
Ms Raeside said that while the school's analysis suggests Year 11 GCSE results are improving, there are still "concerns about underachievement" in other year groups, especially Year 10.
She added that students' set work was sometimes too "undemanding", but praised progress in adapting work to students' varying abilities.
She said: "In history, bright Year 9 students made rapid progress because the work challenged them to think and to produce answers of GCSE standard."
She described behaviour management as "inconsistent" with too much lateness and "drift" at the end of break times.
