The Autism Spectrum Quotient (AQ), developed by the Autism Research Centre, provides a measure of the extent of autistic traits in children.
You can download the diagnostic tests from Autism Research Centre (ARC), Department of Developmental Psychiatry, University of Cambridge, provided that it is used for genuine research purposes, and provided due acknowledgement of ARC as the source is given.
B. Auyeung, S. Baron-Cohen, S. Wheelwright and C. Allison, (2008)
The Autism Spectrum Quotient: Children’s Version (AQ-Child)
Journal of Autism and Developmental Disorders