COULSDON Sixth Form College has been rated 'Good' by the education watchdog, little more than a year after it was deemed "inadequate" for the second time in a row.
The college's jump by two Ofsted ratings comes roughly one year after it was taken over by Reigate College to help it improve.
Ofsted inspectors who visited the Placehouse Lane, Old Coulsdon, college in late February said the quality of lessons and students' attitudes to learning are now "good" and the college is a "very pleasant environment".
They added students are set "ambitious" targets and teachers work "with determination" to ensure students reach their potential.
Steve Oxlade, executive principal of the federation between Reigate and Coulsdon colleges, said the improvement was unprecedented.
He said: "No school or College has ever improved so much, so quickly and been awarded such high grades in a full inspection.
"Ofsted was incredibly thorough, observing almost every teacher, and has now officially not only declared the College out of special measures but concluded that quality is so good that they will be monitoring us from afar from now on, just as they do at Reigate."
The inspectors said the college was not yet outstanding because the students' achievements were too poor until this academic year.
But they added the prospects for this summer's results, the first under the Reigate partnership, were "highly encouraging".
Limited opportunities for work experience were one source of inspectors' criticism, and the range of extra-curricular activities was deemed "too narrow".
But inspectors praised "very significant" improvements in students' attitudes and attendance, which they said had a "tangible impact" on their prospects.
The Under Secretary of State for Further Education, Matthew Hancock, has written to the college to say well done.
He wrote: "I have been briefed on the developments over the past year, and no not underestimate the scale and magnitude of your achievement."
The college's principal, Brett Freeman, said: "Ofsted has seen what we have achieved and recognised that this is something quite unique.
"I have to tip my hat to them because they scrutinised everything that we do."
