The Junior School at Trinity provides a strong foundation to meet the individual needs of boys as they begin their school experience. From the first day at school they are immersed in the Schools' ethos of Mind, Body, and Spirit which will travel with them as they make their way through the Junior, Middle and Senior School. The Junior School Kindergarten to Year 6 is located in a purpose built facility on the Summer Hill Campus.

The development of the Mind is paramount in the life of the Junior School. A differentiated curriculum utilising the Primary Years Programme (PYP) framework allows the boys to develop their potential and have opportunities to succeed at their own level. The boys are engaged in a curriculum that is both stimulating and highly motivating as they are at the centre of all learning experiences.

Sport is an essential element in the life of a Trinity boy, and each boy is given the opportunity to develop a healthy Body. Boys from Year 4 to Year 6 participate in both the summer and winter sporting programme. Year 3 boys have a chance to develop their skills at all of the major sports that the school offers in the Primary School. Sport is viewed as an extension of the classroom and each boy can continue to develop not only his own personal fitness but also the important life lessons of team work and fair play. There are a variety of co-curricular sporting activities for boys to choose from at the Junior School. Most of which are conducted using the state of art sporting facilities on the Summer Hill site.

Junior School boys are encouraged to be part of the co-curricular programme that is offered. With outstanding artistic and musical programmes, along with many other activities, the boys are able to enhance and explore their creative potential. All boys can develop through a wide range of co-curricular activities.

The timeless values of Mind, Body and Spirit are instilled in the boys from the very first day of formal education. At the Junior School, the boys receive a thoroughly Christian education with spiritual qualities in every sphere of learning so that they will "grow in wisdom and stature and in favour with God and man, in order that they may become responsible, contributing members of society."