The inspiration for the College came from local church congregations who became aware of the need to establish an independent, affordable, co-educational College in the developing north-western suburbs of Sydney.

The aim was to provide a high quality education that was academically strong and well rounded, delivered in a clear Christian context. William Clarke College opened in 1988 with 113 students in Years 7 and 8 using the St Stephen’s Anglican Church in Kellyville as a temporary site.

In 2005 the College Council made the strategic decision to embrace a broader philosophy of education. In 2007 the College introduced a Junior School (Kindergarten to Year 4), Middle School (Years 5-8) and Senior School (Years 9-12). In 2015 the College commenced a Preparatory School to allow families in the local community to have a Preparatory experience at the College the year before Kindergarten.

More than a decade on and the College is now a well-established and thriving P-12 school. The decision to introduce a Middle School that at the time served to connect the existing 'secondary' years and new 'primary' years achieved its purpose. As such, from 2018 the College will be structured P-6 (Primary) and 7-12 (Secondary), with the core aim of increasing the focus on teaching and learning outcomes and improving efficiencies.

The support and commitment of the original families was instrumental in the College’s growth and subsequent success. Today, community and parent/carer involvement is actively encouraged and is a pivotal part of College life. The College has over 1500 students and 200 highly professional staff.

The College is named after the Rev William Branwhite Clarke, who was a minister of the gospel and the first incumbent of the Parish of Castle Hill, Rouse Hill and Dural. As well as his parish duties, he was the second Headmaster of The King’s School in Parramatta and a scientist who is remembered as the founder of Australian Geology.