Principal Colin Boxall will be leaving the Bishop of Rochester Academy.

Mr Boxall was appointed as head of school in Magpie Hall Road, Chatham, in late 2011 and took up his role full-time in Easter last year.

The exact reason for his departure is unclear at this stage, and will come as a surprise to many.

Mr Boxall will leave at the end of the summer term.

Deputy Kuljit Rahelu will take over as acting principal with immediate effect.

Mr Boxall was tasked with turning around the fortunes of the academy, which endured a difficult beginning after opening in September 2010.

The first principal, Christopher Sweetman, resigned after being suspended following a number of incidents, including a fight between two girls which led to the police being called.

In 2011 the school had the third worst GCSE results in the country.

A year later these results dramatically improved, coming in above the government benchmark.

A letter from the school to parents said: "The academy sponors acknowledge that, under Mr Boxall's leadership, the Bishop of Rochester Academy has improved its performance and demonstrated that it can deliver for its students and the local community it serves.

"We look forward to building on this foundation, working with governors, staff, students and parents to ensure that the academy continues to improve and becomes a centre of excellence for secondary education in Medway and the south east."

Cllr Tristan Osborne (Lab), whose ward includes the school, said the news came as a "bit of a shock".

Chatham MP Tracey Crouch said she was "shocked and disappointed" and added: "Mr Boxall was making good progress and had some really good plans for the future."