A total of 515 pupils have enrolled at Markethill High School this year, prompting calls for a new building and sixth form to become a priority.
Principal James Maxwell said the school has now become the biggest non-selective controlled school for pupils aged 11-16 in the Armagh, Banbridge and Newry City areas.
He, along with the Board of Governors and the community have been leading a campaign since September 2012 for the school to cater for pupils beyond the age of 16.
The school was oversubscribed for Year 8 places this September by a record 31 places. However, in May it was granted a much-needed temporary variation for an additional 16 pupils, as many of the children applying lived closer to Markethill High than other suitable schools.
Said Mr Maxwell, “In June 2014 we were apparently turned down for a new build by then Minister John O’Dowd because we did not have 500 pupils. That is no longer the case.
“Furthermore, the astonishing results our pupils and teachers have delivered this year at GCSE, with 90 per cent of pupils attaining five or more passes at A*-C, should place this school again as a top, leading non-selective controlled school.
“It is now completely unacceptable that a school with one of the best pass rates has to let go of 100 or more pupils at age 16, putting at risk their academic and pastoral wellbeing. We must, quite simply, get sixth form status in the near future.”