The aim of the survey was to provide a picture of the school readiness of 5-year-old Montréal children starting school and to identify disparities between neighbourhoods and the socio-economic factors determining these differences. 10,513 children were assessed using the Early Development Instrument. The results show that in Montréal, one child in three is vulnerable in at least one area of school readiness. Figures range from 22% to 43% in the different territories. A significant association was found between parents' level of education and the vulnerability of children. Differences between languages are found when analyzing school readiness based on groups of children by mother tongue. A comparative analysis between Montréal and two other large Canadian cities shows that the average score of children in Montréal is higher than the average score of Vancouver children in all areas and higher than the average score of Toronto children in two areas. The differences between territories in Montréal raise questions about public policies and inequalities in access to services and resources between affluent and less affluent neighbourhoods. A comparative analysis between Montréal and two Canadian cities provides a nuanced view of the perception of child vulnerability in Montréal when compared to the rest of Canada.