The heterogeneous nature of Autism Spectrum Disorder (ASD) makes accurate diagnosis challenging. Best practice assessments in schools can open pathways to appropriate interventions and educational placements for those with ASD, as well as help identify a student's strengths. There are various tools used in school settings to assess autism. In this review, we briefly discuss those instruments with a specific focus on the use of the Autism Diagnostic Observation Schedule-Second Edition (ADOS-2), one of the most widely used and well-researched assessment tools. We address special considerations that may impact the psychometric properties of the ADOS-2 as well as outline practical implications and recommendations for practitioners in schools.