Hello and thank you for asking such an important question.  There are several factors that could be responsible for your sons academic difficulties.
 
 First, I think you need to ask if his progress has been recently reviewed by a complete educational team within the last year?  If not, then you need to request one (in writing) and ask for the team to include the school psychologist, special education teacher (s) and classroom teachers ( if he is mainstreamed). It is my experience as a School Psychologist that sometimes children will be able to be successful in the elementary grades, but once the school material becomes much more involved and requires more independent learning the student demonstrates increased difficulties.  Also, textbooks create a larger challenge as the print becomes smaller, the types of questions can be much more difficult and the amount of work expected to be completed each day can increase, as well.  Students who have difficulty with school can become more frustrated, unmotivated or "shut down" because they have hit a "wall" and don't know what to do to get back on the track to success.  
 
If new evaluations are warranted then they may shed information about his current learning abilities and cognitive strengths and weaknesses.
 
Second, ask yourself has your sons motivation changed in school?  Does he seem more distracted?  Is he completing classwork and homework or "forgetting" and "losing" assignments?  Sometimes, the onset of the teen years can be a reason for not "learning " in school because focus can be elsewhere. Also, he may have some other issues that need to now be addressed by a physician.  
 
 Third, are there other changes in his day to day behaviors?  Does he seem more alone?  Has he become more engaged in extra-curricular activities and not caring
about school?  While some of this is very normal teen behavior a radical change in behavior should be addressed by professionals, such as the school counselor/ your son's physician.
 
I am adding a useful link for the national organization for learning disabilities.  Also, this website (www.education.com) has an excellent middle school section to help with strategies, as well.
 
Good luck!
 
Louise Sattler, NCSP
Owner of SIGNING FAMILIES
www.Signingfamilies.com

I think it’s safe to say that help is on the way! Good for you for looking beyond the IEP process and taking a close look at how your son is faring in school, especially during times of transition. Moving from one grade to the next can be difficult for students with LD, and middle school, in the best of circumstances, opens a Pandora’s box of challenges! Some hurdles have to do with increasing expectations for achievement, some deal with the social/emotional turmoil that often typifies the early adolescent years, and some reflect the changing nature of how LD impacts youngsters as they becomes more insightful about their personal journeys through school and the particular nature of their struggle. Some reflections and suggestions:
 
--Reach out to your son’s teachers, share your concerns and gather information about what might be contributing to his diminished progress over time. Then share what you have learned with teachers and members of the IEP team! (Yes, you can request that a meeting be convened for this purpose. Visit NCLD’s online Publications area for helpful guides, including one on IEPs.)
 
--Talk to your son and encourage his participation in relevant discussions and planning. Eighth grade is the ideal time to begin to include students in planning conversations with school personnel. Bolstering your son’s understanding of his LD and allowing him to first listen to and then participate in problem-solving discussions about available resources and accommodations will help him to hone the self-advocacy skills he will need as a high school student and then later when  he transitions to postsecondary settings such as college or the workplace.