In the short term - don't hassle him, or make him do anything that looks at all like school. He needs to get over the feelings of stress and failure first. You can think of it like the long summer holiday if that helps - a chance to unwind and think about other things.
When he does feel like doing a bit more, try not to think in terms of "school subjects" as this is likely to only stress both of you. Instead, think of what you hope he will get out of this whole stage of his life - that's what "education" is about, not neat little sections with a test at the end.
So at his age you probably still want him to be improving his reading skills, reading a variety of different kinds of things and picking out relevant information from them. And improving his numeracy - that might be thinking about the practical uses of numbers, like sorting out busfares and checking change, or it might be more complex stuff, depending on his interests. And presenting information that he has pulled together - that might be making up a project file, or a Powerpoint presentation, or a huge wallchart. It might include written info, diagrams, graphs, whatever, or it might be something more imaginative.
Add in something that allows him to be creative (could be art, could be writing computer programs, could be icing cakes!), and some exercise, and he'll be getting an education suitable to him, which is what he needs.
It's fine if he gets all the things I've mentioned by reading up on WWII tanks, or the Pyramids, or Warhammer, or any other subject that he finds interesting - you have to let him start from what is interesting to him, and encourage him to develop useful skills from it, rather than trying to force him to show an interest in reading "Jane Eyre" or whatever just because it is on this year's syllabus. From my (little) experience of Aspergers, he will find some subjects fascinating, and others utterly boring and pointless, and not have much ability to pretend otherwise. School will be failing him because they expect their pupils to have (or at least pretend) a moderate level of interest in everything they are told to learn. You don't need to start from there, as you only have one "learner" to encourage, so work with who he is rather than a package of one-size-fits-all, and he'll be fine.