what i have found to work for me is music. a headphone set doesn't offer the visual distraction and keeps a separate part of the mind active. it also gives you something enjoyable to do with the not-so-enjoyable. i only say this because it worked for me. i was diagnosed with ADHD as a kid and believe myself to still suffer the effects now.
**You might try some Australian Bush Flower Essences Cognis might help for better attention span. & drops in a 16 bottle of water, shake and sip as he is studying and when taking tests for better recall. NOT a drug and no bad side effects :o)))
"Australian Bush Flower Healing" by Ian White
ISBN-10: 073380
Yahoo email group discussing Australian Bush Flower Essences
http://health.groups.yahoo.com/group/ABFEstudy/