First inspectors published a report describing St Frances Xavier college as outstanding. Then students achieved a 99 per cent pass rate in their A-levels, with three obtaining the grades needed for Oxbridge universities.
Principal Bernie Borland expects the results to keep SFX at the top of the college league tables for inner and south London.
For the past two years since comparisons were made with local schools, the college has also out-performed all state schools with sixth forms in Wandsworth, Lambeth and Southwark, except one.
Mr Borland said this has been achieved despite the fact that four- fifths of its students are from "widening participation" postcodes, inner-city wards considered to be areas of high deprivation. The same number are from black or ethnic-minority backgrounds, with half of that intake being Afro-Caribbean, the lowest-achieving ethnic group nationally.
Ofsted's inspection report said "Overall, students do much better in exams than predictions based on their performance at GCSE.
"A very high proportion of the teaching is good or very good. There is an unremitting focus on students, their progress and the effectiveness of teaching."
Mr Borland said that SFX takes about a dozen students most years who have been rejected by school sixth forms because the GCSE passes were not considered good enough. "This is a very comprehensive college," he said.
"We take youngsters who have been through the Lambeth and Southwark education systems. Our students come from the kind of underprivileged backgrounds traditionally associated with failure.
"We have students achieving very high A-level grades alongside youngsters taking level one and level two vocational courses. It gives a lie to the belief that you can't educate more able students alongside the less able.
"We have lovely inner-city kids who come from quite different backgrounds who have attained at the very highest level."
Students like Charissa King, who has a place at Cambridge to read English, Sean Leopold, accepted by Oxford to study human sciences, and Alice Doyne, also offered a place at Oxford to study history.
"Our value added is fantastic," he said. "But that doesn't get good jobs or places at the best universities. If we push them up to grades C or D, that might be an achievement, but we have to insist these youngsters get higher grades that get them into Russell Group universities. We are very tough on them. A key issue is their attendance and punctuality. We have to be on their backs to ensure they work hard, and they take it.
"But we are quite relaxed in other ways, certainly more relaxed than a school environment."
He said that recruitment and retention of staff is not a problem, despite the fact that salaries are higher in nearby schools. "The staff are dedicated, hard-working professionals who don't let up," he said.
Of the annual grade inflation debate, he said: "It is very important to be optimistic about young people and what they can achieve, and not to decry the effort they put in to tackle quite difficult exams."