The use and interpretation of appropriate social skills are necessary for successful functioning in everyday life. For individuals with Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD), impaired social functioning often has a detrimental impact on everyday life situations. While it is evident that many students struggle with social communication, it is often difficult to assess these deficits when determining the need for services in the educational setting. Formal assessments present a challenge in evaluating a student’s social thinking ability. Furthermore, many students with disorders in which social impairment is characteristic often present with average to above average intelligence and perform well on standardized assessments, making it difficult to justify the need for intervention even though their deficits in social aspects of communication are readily apparent. The purpose of this study is to investigate the effectiveness of the Social Thinking Dynamic Assessment Protocol in identifying deficits as well as differences in social functioning among three groups of students with ASD, ADHD, and typically developing students. Results showed marked differences in social functioning between the group with ASD and the control group. Results also indicated areas of deficit in the group with ADHD. Similarities in deficits were noted between the groups with ASD and ADHD. The findings from this study support the use of an informal dynamic assessment when evaluating social skill ability in students with suspected deficits. Improving assessment methods for identification of social skill impairment is likely to benefit students with ASD, as well as students with ADHD and other developmental disorders not typically treated for social impairment because it will allow for more in-depth investigation into social and cognitive functioning aspects of social language use.