What should I expect the school district to do in terms of testing, evaluation, and treatment? Should I get my son OT, speech/hearing evaluations, and treatments on my own? Would play therapy help him? I just need a starting point and a plan, but am so overwhelmed I just don't know where to begin.
There are some excellent websites where you can get more information about NLD as well as help in finding appropriate supports for your son. Have a look at Nonverbal Learning Disorders Association, or NLDline. If you can hook into a network of other parents whose children have NLD, you can begin to explore effective resources in your community for help.
Now to your specific questions: If you have a good Child Study Team in your school district that can review the results of the testing you've already done, they may be able to recommend services that your son could have during school time, like occupational therapy. You can also request a speech and hearing evaluation, although if you suspect central auditory processing disorder, it is usually helpful to have an audiologist do a comprehensive evaluation also. That specialist may not be available in every school district.
Unfortunately, many district evaluation teams don't evaluate children until they have failed academically. Some even have an unwritten policy that prevents them from testing children below a certain grade. As a parent, however, you have a legal right to request a free evaluation as well as services and accommodations that your son might need. Speech and language therapy, occupational therapy, and counseling are three services that schools usually provide free of charge for those who require them.
If you have any difficulty getting the services you need, call the Learning Disabilities Association of America at 1-888-300-6710, National Center for Learning Disabilities at 1-800-575-7373, or have a look at Schwab Learning. Someone there should be able to guide you through the system to get appropriate help for your son.
As for play therapy, it could be a part of your son's comprehensive treatment plan and could aid his socialization skills. This is usually not a service that is provided in school, however. You can ask if the guidance counselor at school provides a group counseling session where children can practice their social skills with others.