Steve DownesOne of the city's longest serving high school headteachers has stepped down- a few months before he was due to be replaced when the school becomes an academy.Steve Downes

One of the city's longest serving high school headteachers has stepped down- a few months before he was due to be replaced when the school becomes an academy.

In a letter to parents, pupils and staff, Costessey High head Philip May spoke of his 'pride' at leading the school since 2001.

He also opened his heart about the 'betrayal' of the school and its students by former deputy head Stephen Brenchley, who in 2006 was jailed for five years and three months for sex offences against two of his former pupils.

Mr May said the 'destabilising' effect of the offences led to the exodus of more than half of the school's teachers, triggered plunging results and pushed Costessey High into special measures for the second time in a few years.

But he spoke of his delight at how the school and community pulled together to haul it out of special measures after the shock of the Brenchley case - having made a similar effort in 2002.

Mr May's departure comes after he missed out on landing the role of principal-designate of the �20m academy at Costessey, which is expected to open in the existing school buildings in September.

Lead sponsor Ormiston Trust, the governors and Norfolk County Council decided instead to appoint Rachel de Souza, who will move from her current role as principal of Barnfield West Academy in Luton from September.

In the interim, the school will be run for half a term each by current deputies Samantha Penn and Andrew Sivitter.

In his letter, Mr May said: 'I am writing to tell you that I have decided to leave Costessey High School. From March 31 I will no longer be headteacher.

'I believe this is the right time to step aside, as plans for the school to become an academy progress.'

He added: 'At the open evening in October 2000, before I took up post, I told the prospective parents that I was proud to become headteacher of Costessey High School. Despite the ups and downs of the past nine years, I have never ceased to be proud of this school.'

He said he had had some 'memorable experiences', including:

t watching 2003 school production Les Miserables - 'the best show I have seen at any school'

t watching the girls football team twice narrowly lose a national cup semi-final

t standing on a Viking longship under construction

t seeing young people fulfil their potential and go on to good jobs or higher education.

Mr May said he was proud of how the school sixth form had gone from potential relocation to the then Earlham High to staying were it was, growing from 85 to 160 students and achieving a 'good' Ofsted rating.

He highlighted the two escapes from special measures, the achievement of science specialist status at the first attempt and recent GCSE results that were an all-time high - with 59pc of students getting five or more A*-C grades and 41pc getting five good grades including English and maths in 2009.

On a sombre note, he said: 'The betrayal of the school and its students by the deputy headteacher was a terrible crisis, which would have destabilised any school.

'The trust of young people and their parents was profoundly affected. Nearly half of the teaching staff left as a direct result of their horror and shock. Results dropped in all core subjects. Despite this, I am very proud of the staff who stayed and the staff who joined to turn the school back around.'

He concluded his letter with a firm endorsement of the change to academy status, which looks almost certain to be approved after being supported by more than 90pc of respondents in a recent public consultation.

He said: 'I am delighted that Costessey is set to become a separate 11-18 academy with an experienced sponsor. An academy can further improve behaviour and take results still higher.

'I have been honoured to lead this school over the past nine years and I wish it all the best for the future. After a few weeks' teaching, to fulfil my commitment to my English examination students, Mrs May and I are retiring to Sheffield to be near our family. You can be sure that when the results come out each year, I will be very happy to see the academy's continued progress.'

t To read the full letter, visit www.eveningnews24.co.uk.