​​1984 saw Aquinas College reach its peak enrolment of 707 students, requiring a staff of fifty to administer the school. After this time, the development pattern of the school changed. Other Catholic schools opened on the Gold Coast and the opening of Guardian Angels Primary School adjacent to the college, meant that Aquinas became a secondary school only. As a Parish school, Aquinas College had been conducted by the Christian Brothers from its foundation in 1963 until 1987. In 1988, with the Brothers withdrew, and the administration of Aquinas College entered a new era with the appointment of its first lay principal, Mr Ed Riley. At this time, the college’s enrolment was 440 boys.

One of the most dramatic and controversial announcements in the history of the Parish was made in 1990, when the Sisters of Mercy announced the closure of Star of the Sea College. To cope with the needs of the education of the girls, Aquinas College became a co-educational school, with the first girls attending in 1991. This move demanded a tremendous financial commitment from the parish to the building of new facilities, (including a new library completed in 1990), and remodelling of old ones. Under the leadership of Aquinas’ second lay principal, Mr Terry Enright, the college’s enrolment rose again to over 600 students.