Student wellbeing is of central concern for parents/caregivers and teachers and for state and national governments. In Australia in recent times several major initiatives have been undertaken to address the area of student mental health, including the KidsMatter Initiative. Across 2007-8 a trial of KidsMatter was carried out in 101 schools across Australia. Part of the roll-out of KidsMatter was a detailed evaluation of its implementation. Thus, in this paper we report on findings associated with the implementation of the KidsMatter Initiative. Underpinned by a framework of quality, fidelity and dosage we used Latent Class Analysis to create an Implementation Index, which was used to classify KidsMatter schools into high implementation and low implementation categories. Profiles of the high and low categories provide insights to the characteristics of successful and less successful implementation. This analysis shows the influence of factors associated with both the KidsMatter initiative and the environments in the sites where KidsMatter was implemented. [Author abstract]