Shrewsbury School is to admit girls into all classes from 2014, it was revealed this afternoon.
The private school is aiming to become fully co-educational by September 2014, having already introduced girls to its sixth form in 2008.
By 2020 about 35 per cent of the pupils at the school are expected to be girls.
The move to co-educational status is part of the private school's new 2020 development plan, which will also include a multi-million investment in refurbishing and creating new facilities.
Headmaster Mark Turner said: "The move to educate girls in the sixth form was controversial in 2008 but the experience and results have proven the wisdom of that decision and few would deny that the school is a stronger and more successful community today.
"In September this year we admitted a record number of pupils, which shows that parents value the 'Shrewsbury experience' and the direction we are taking."
Chairman of governors Richard Burbidge said: "The plan builds on the school's traditions and ethos, which have evolved since our foundation in 1552, and places these in the context of the increasingly competitive and challenging world for which we need to equip our pupils, by providing them with best possible 'all round' education."