Background: Assisting children with delays and disabilities to develop skills that will maximise their chances of success in regular education classrooms has become important with the trend to inclusion. This study examined (1) the essential skills for successful integration nominated by teachers, (2) the relationships between teacher perception and child performance on selected skills, and (3) the relationship between teacher perception of integration success and selected skills. Method: On-task behaviour and direction-following skills of 33 children with intellectual disabilities were measured following one term in regular kindergarten. Teacher perceptions of children's skills were measured after one term and again at the end of the year. Results: Skills nominated by teachers as being critical to school success were generally related to classroom, social and self-help skills. Children rated by their teachers at the end of the year as being more successfully integrated had better on-task behaviour and responded better to group directions than those rated as less successful, but the relationship between the direct and indirect measures of classroom skills was generally weak. Conclusions: Critical skills identified were similar to those identified in previous research, suggesting that these findings may be considered robust. The weak relationship between the direct and indirect measures of classroom skills raises questions about interpretation of research that relies entirely on perceptions of teachers. The findings of the research have implications for provision of preschool and early school services.