Educating the children of Belfast has always been the school's main aim, however before 2004 the school could only provide 5 years of secondary education. This was a result of the school's structure as it could not hold more than 750 pupils. The maximum year that a pupil could reach at the school was Year 12 (5th year). While in 5th year, the pupils would complete their GCSEs and await their results. After each pupil had received their GCSE results, they would then have to go in search of another school (secondary or grammar) that would accommodate their need for further education in the form of AS- Levels and A-Levels. The main choice, of course, was St Mary's Grammar School.