Activities such as music, art, dance, drama, debating, sport and strong participation in the Duke of Edinburgh's Award Scheme are included in the co-curricular program.

The school facilitated the growing demands of the community in the newly created East Killara.

The name: "Killara, an Aboriginal word meaning permanent" The castle: A permanent place, shelter and reassurance, a means of maintaining that which is worthy of preservation, a storehouse of knowledge The key: It is a symbol of progression, which opens doors of learning.

It is also an emblem of growth and development into adulthood The escutcheon: Provide protection, a pivoted keyhole cover The motto: Latin: Conserva Progredere, symbolises preservation of the best of the past and continued development into the future Dr Mark Carter, a local boy and former student of the school, was the principal from 2002 until 2013.

She was previously a teacher in the HSIE Faculty at Killara, but had more recently served as Deputy Principal at Pennant Hills High School.

Each block contains around the same number of classrooms (12 to 18) as found at other North Shore public high schools.

Other facilities include the Kerrabee Centre, which comprises a large hall capable of seating more than 1000 people and a 250-seat performance theatre with state-of-the-art sound and lighting, a small oval named jubilee, four multi-purpose courts, a large quadrangle, and a small residential buildings called the house, which has since been demolished to build a new block (Block K).

Capital works since 2003 have resulted in the installation of security fencing, and five COLAs (Covered Outdoor Learning Areas) built around the school, grounds enhancements, upgrades to science laboratories, classrooms and the construction of studios above the canteen.

G block opened in 2014, containing specialist technology and art rooms, and a number of general learning spaces.

Killara High was the best-performing public comprehensive top non-selective government school in the state for years 2000–2007, 2009–2011, 2013–2015 and 2022 by HSC performance.

These include: Many Killara High School Students in various Years participate in the Rotary Youth Exchange Australia, sending them to many parts of the world.

Meetings are scheduled for 7:00 pm on the third Wednesday of every month, except where this clashes with vacations or school activities.

An annual award ceremony is held to acknowledge the sporting and academic achievements of the students at the school.

A detailed map of the local enrolment area and street names can be found on the school website.

In 2015 a shared school development day was held at KHS, called Killara Connect.

The NS5 unites KHS with Chatswood, Ku-ring-gai, St Ives and Turramurra High Schools.

Many students report that visiting Menindee is one of their most important experiences of their secondary school years.