This video was telling. If you notice, the girl had signs of higher stress. She also has less eye contact, which sometimes is interpreted as being disinterested.
Although eye contact is not an indication, many children with ADHD have poorer eye contact with their peers.
Also observe the use of pronouns: when asked what she would like those without ADHD to know, her response was something like "That they can listen better". To her, it is clear that the "they" refers to children without ADHD. However, this is not always clear to the audience. It has been found that children with ASD (and ADHD) have more irregular use of pronouns as compared to their peers. This can make communication challenging, since they believe they have already been very clear.
When teaching children with autism or ADHD, it may be helpful to focus more on pronoun references, since these are typical problem spots for such children