When my children, both inattentive, were pre-schoolers I thought that they had amazing attention spans. They would sit for hours with play-dough, drawing, in the sandbox, playing with barbies, trucks etc.
By 1st grade, teachers were concerned with my son's ability to attend. I could not believe it! After exhausting every other possible cause and remedy for ADHD-in, he trialed stimulant medications at age 8. The results were positive, immediate and dramatic.
Looking back, I think my kids' ability to sit for long periods of time was a result of their inattention. They would play a bit, look up, let their minds wander, go back and so on. (this is what homework looks like!).
I am not saying that being able to sit for a long time indicates inattention - just that for kids with ADHD-inattentive, the red flags can be confusing.
And, as Grinity mentions - there is a genetic component. As I look around both sides of the family, I see many relatives that are most likely undiagnosed with ADHD. Now that my kids are older, the symptoms are a bit more clear - difficulty sustaining focus on a single task (and focus and distraction is easier to see), forgetfulness, lack of planning.
