It sounds like you need to begin by having a comprehensive evaluation done that will address not only your son's learning needs, but also his behavioral and emotional ones. You say he's on a different curriculum, but I'm not sure what that means. Has he already been evaluated? If not, my first move would be to get as much information as you can about what his special needs are. You have the right as a parent to have a free evaluation done at your local school or school district. If you have trouble getting this done, see if there is a parent representative at your school district who can help you. If that doesn't work, contact one of the toll-free numbers of a learning disabilities advocacy group like Learning Disabilities Association of America 1-888-300-6710 or International Dyslexia Association 1-800-ABCD123. Ask if either of them has a branch in your community. Someone there should be able to walk you through the process of evaluation and also let you know what programs are available to you locally for the summer.
Frequently, colleges or universities sponsor free or reduced-fee tutoring over the summer and/or during the school year, where graduate students in training to be teachers work with kids one-on-one under a professional's supervision. If you can afford to pay a private tutor, ask the head of the college's learning disabilities or reading program for a recommendation.