The World Health Organization has encouraged a whole-school approach when trying to promote mental health and well-being in schools. The Internet-based School Well-being Profile aims to be a holistic well-being evaluation tool for schools. Well-being is divided into four categories: "school conditions", "social relationships", "means for self-fulfillment" and "health status". The questionnaires for the School Well-being Profile were developed for school personnel and for pupils at three levels: primary, lower secondary and upper secondary schools. The present data consisted of the responses from 8285 participants from primary, lower and upper secondary school pupils in the school year 2004-05 in Finland. School well-being was compared between gender, school levels and grades. Pupils in primary school experienced school conditions, social relationships and means for self-fulfillment to be better than pupils in secondary schools. When comparing gender and grades, the main finding was that girls and younger students within each school level rated school well-being more positively, except the fact that boys had fewer symptoms than girls did. The aim of the School Well-being Profile is to provide a well-being evaluation tool for schools to use. The idea is that schools evaluate their well-being, make positive changes and perform the evaluation again to see if progress has been made. (Contains 2 tables and 2 figures.)