A 3 mile hike, you expect my son to be the straggler who struggles. Instead, halfway through - he's the one leading his peers and even overtaking some of the grown ups. Chances are he can out hike, swim or even run most grown ups.
Don't assume (Ass-U-Me after all) what he can comprehend...he may be struggling to grasp angles, division and grammar...but is methodically working his way through (on his own no less) Tolkien's "The Hobbit."
Don't think he isn't listening to you...so watch what you say. He has an almost word for word memory for what people say and will bring up conversations days later, that he's heard. This can lead to sometimes funny and very often, awkward explanations of the meaning of those conversations.
Don't second guess him, do not lower that bar, do not expect less of him and most of all...never ever think he doesn't have as much to contribute as you or I. Don't be surprised, at what my son can do.