Objectives The identification of intellectual disability in children can help them access targeted support and interventions. Research suggests that current methods of identifying intellectual disability in schools in the United Kingdom need to be improved. Screening tools can play a role in this. The study examined the performance of the Child and Adolescent Intellectual Disability Screening Questionnaire (CAIDS-Q) in mainstream schools as a means of facilitating identification of intellectual disability. Methods Parents and/or teachers of 70 children completed the CAIDS-Q and an assessment of adaptive functioning about them. Children who were indicated as having difficulties completed an intellectual assessment. The data were used to explore some psychometric properties of the CAIDS-Q. Results The CAIDS-Q had sensitivity and specificity values of 100% and 79% respectively when completed by teachers and 92% and 70% when completed by parents. CAIDS-Q scores correlated positively with intellectual and adaptive functioning scores, with large and medium effect sizes respectively. There was moderate agreement between parents and teachers on the outcome of the CAIDS-Q. Conclusions The CAIDS-Q, when used in mainstream schools, had psychometric properties consistent with those found in health service settings. It may offer a way of improving identification of intellectual disability in educational settings.