I see the inattentive stuff with my difficult child when her anxiety is up. Think about something that makes you really nervous or anxious. (The thing that scares me most is public speaking. bleck) How do you react? With me my heart races, I get a ringing in my ears, an inability to focus on the simplest tasks or conversation and sometimes I feel like I can't catch my breath. And my anxiety is nowhere near as bad as my daughter's. Then, she will focus in on other things: a student tapping his/her pencil or feet, shuffling papers, etc., to the point of not being able to focus on anything else.
If allergies are acting up and he's not feeling well, that's not going to help either.