Hi RayJay, sorry we missed your post. I am on my ipad with not as much access to links, bur to get you started go to app. B here to find where your son's scores fall:
http://www.nwea.org/sites/www.nwea.org/files/resources/NWEA_2011_RIT_Scale_Norms.pdfP.69 shows his math score to be 99th % for 6th graders, 98th for seventh, 92nd for 11th...
P. 57 shows his reading to be 96th % for 6th graders, 94th for seventh, etc.
Your son's scores are great. I'm not sure what to suggest re: summer, except encourage him to read. I have an 8yo and we haven't really done much in the way of academics in the summer. just how our family does things. However we encourage things DS enjoys, provide interesting excursions, etc. He wants to learn programming, so we'll help guide him there. hopefully someone with a kid doing algebra will chime in with math fun recommendations.