Archbishop Lanfranc School is to be absorbed by an academy provider that runs two other Croydon secondaries.
The school, in Mitcham Road, will become an academy sponsored by the Coloma Trust from September.
The trust already runs Coloma Convent Girls' School, the highest performing state secondary school in Croydon, and Quest Academy, formerly known as Selsdon High.
Archbishop Lanfranc is among the borough's worst-performing and recorded the lowest GCSE pass rate at grades A*-C last year.
The Archbishop Lanfranc Academy, as it will be known from the next academic year, will be led by headteacher Michael del Rio, supported by Quest Academy's executive principal Andy Crofts.
Maureen Martin, headteacher at Coloma Convent, will oversee all three schools.
She said: "The new Archbishop Lanfranc Academy will provide an opportunity for The Coloma Trust to extend its positive, life-changing reach to hundreds more Croydon school-children.
"The high standards and expectations that have brought Coloma students such success over the years, have proven to be transferable to other school environments.
"We have seen it in the progress being made at the Quest Academy and we intend to see it again at Archbishop Lanfranc."
The trust plans to introduce a sixth-form at the school, which is already slated to receive multi-million Government funding to replace its dilapidated building.
Coloma Convent is consistently among the top performing schools in Croydon and achieved a 95 per cent A*-C GCSE pass rate in 2013, while Quest Academy's 16 percentage point rise was the highest in the borough last year.
However, Coloma Trust is one of three academy chains in Croydon embroiled in the mystery of pupils "disappearing" in the year before they sit GCSEs.
Quest Academy saw Year 11 pupil numbers drop 10.9 per cent in the 12 months before theirs exams last year - the second sharpest drop in the borough.
The figures led David Clark, departing headteacher at Archbishop Lanfranc, to call for an investigation.
He said: "If pupils are being removed from school rolls for less than good reasons, it raises more serious questions about a climate and system which encourage people to the view that it is OK to do so.
"What needs to be understood however is that, if children are being removed from school rolls without following due process, this represents a major safeguarding issue which is potentially more significant than league table positions."