ADHD is one of the first things that’s suspected when a child’s behavior in class, or performance on schoolwork, is problematic. But these are also behaviors that can be a result of other factors, from anxiety to trauma to just being younger than most of the kids in the class, and hence a little less mature.
That’s why it’s important for teachers and parents both to be aware of what ADHD looks like in the classroom, and how it might be confused with other things that could be influencing a child’s behavior.

A few guidelines here, from the Child Mind Institute