I definitely recommend the book Smart But Scattered Teens by Peg Dawson and Russell Guare. It is excellent and explains Executive Functioning Skills. There is a self-assessement and parent assessment in it that will help identify EF strengths and weaknesses. There are tips to help with the weak areas. Be patient, this is going to take some time. Also see if your stepson can think of some peers with whom he could create a study group. He may need study guides or to make flashcards. There are also many online tutorial sites and HW help sites. Wishing you the strength to persevere….this is a process!