Attention is an essential mental process that is important to achieve learning progress. We cannot get better in our academic learning unless we concentrate our attention on the person giving the educational material, such as the teacher or trainer. Children with Autism Spectrum Disorder (ASD) may have attention difficulties that can directly influence their academic skills. In recent years, robot intervention in autism therapy and assessment is becoming a popular research topic due to its role in enhancing children's attention more than a regular human therapist, as well as, the increasing number of autism children compared to the availability of professional therapists. Robot intervention helps in reducing therapy time and makes early therapeutics sessions easier and much promising. Many researches have been conducted to develop robot intervention techniques for ASD children, and some methods have already been used to assess autistic individuals' attention during the robot intervention sessions. Yet, the existing attention assessment methods are either very complex or simple with one measured interaction cue only. This paper presents a practical and low-cost automatic approach to assess autistic individuals' attention during robot intervention; addressing multiple interaction cues. Experimental results show that the proposed attention assessment system could accurately measure the child attention and enhance therapy progress. This automatic attention system can open a new era for utilizing technologies to monitor students' attentions in the class to enhance educational systems.