A-level students who had their places at a grammar schoolwithdrawn after failing to achieve certain grades will now be allowed to return.
The decision was welcomed by Orpington MP Jo Johnson, the Science and Universities Minister, who called it a "sensible move" by a "great school" on Twitter.
After the U-turn, St Olave's, in Orpington, south-east London, said its goal has always been to "nurture boys who flourish" and help them fulfil "their full potential academically and in life generally".
Legal action was taken against the governing body of the high-achieving school after two students were told they could not continue their A-level studies into Year 13.
The pupils, who cannot be named for legal reasons, failed to achieve Bs in any of their subjects taken in the first year of sixth form, lawyers said.
Dan Rosenberg, from Simpson Millar solicitors, who has been acting for the families, said he was "pleased the school has agreed to readmit the children and withdraw their policy".
He added: "We would now expect all other schools with similar policies to do the same".
The school said in a statement: "Following a review of the school's policy on entry to Year 13, the headmaster and governors of St Olave's Grammar School have taken the decision to remove this requirement and we have today written to all parents of pupils affected to explain this and offer them the opportunity to return to the school and continue their studies.
"Our aim as a school has been and continues to be to nurture boys who flourish and achieve their full potential academically and in life generally.
"Our students can grow and flourish, making the very best of their talents to achieve success."
The school, which will start its new term on September 5, is said to operate a three-pronged policy to "maintain its exceptional A-level results".
Year 12 pupils will normally have gained three Bs or higher if they wish to complete their studies in Year 13, the school's sixth form rules and regulations state.
An email sent to the school's Year 12 tutors in June said that pupils who scored a C would not be able to pursue that subject through to A-level.
If a student scored a C, they must sign an agreement that the school reserves the right not to enter them for A-level examinations in any subject in which it is considered they will not score a B or above.