A head who attacked an author’s use of dodgy figures to bash his school has won the backing of parents.

Andrew Penman criticised Rutlish in a newspaper article promoting his new book about finding a good state school for his son.

But Alex Williamson, headteacher at the Merton Park secondary, has criticised the writer for doing down the school’s success.

Mr Penman said he was forced to move to Surrey in a bid to find a good quality comprehensive school, and for two years had considered pretending to be Catholic to win his child a place at nearby Wimbledon College.

In Saturday’s Guardian article he claimed the latest exam results show only 49 per cent of pupils at Rutlish, which had been his son’s nearest secondary, achieved five GCSEs including English and maths - the actual figure is 61 per cent.

Commenting on the story in a message on the Guardian’s website, Mr Williamson wrote: "It is disapointing that a local resident is not prepared to support his local school and be aware of the rapid improvements taking place.

"It is also disapointing that he is prepared to write such an article without referring to the school to ensure that his information is correct."

The author said he wrote off Rutlish after a friend claimed he had seen a pupil acting agressively during a visit to the school.

He also claimed “rubbish” results at Southfields College were because too many pupils spoke English as a second language, and Tooting had “too many murders” for his son to go there.

One commenter, tracynewby, wrote: “Shame on you Guardian, printing an article of an arrogant man's attempt to damn a school he has not even personally visited.

“I would like to thank the head and all the staff of Rutlish School for all the hardwork, effort and enthusiasm they have shown during my son's first year at Rutlish.”

Merton Council’s cabinet member for education, Peter Walker, said: “Merton schools are good, and like most other state schools improving rapidly thanks to the investment they have received in recent years and the efforts of our children and teachers.”

The council said its schools were improving, with the percentage of pupils achieving five GCSEs including maths and English rising by 5.6 per cent this year.