I wrote the end of High School, the end of dreams six months ago. Before and since I've been thinking about how to explain to #1 why he isn't going to get a (true) High School diploma, and why he won't be going to any of the Colleges he loves to dream about.
I think most would agree that this is not an easy conversation.
Fortunately he has given me time to think. He approaches the topic from time to time, but usually veers off. I think I now have a story that is true but leaves some hope and a direction.
The key is that he has many cognitive and behavioral disabilities. Some are more amenable to improvement than others. There's not much, for example, he can do about his base IQ. So I'm not going to talk about that; I won't say 'there are some things your brother and sister learn quickly that you cannot learn'.
I can, however, talk about disabilities that I expect to improve with time and effort. One his core disabilities is difficulty persisting in tasks that he does not enjoy. For example, he has always been a relatively talented hockey and baseball player -- but he is very inconsistent at practicing. Lack of practice means he plays at a C or rec level rather than at a more competitive level.
Of course his hockey or baseball activities, though important for his life, aren't my key focus. They illustrate a broader problem that has biological roots in cognitive fatigue and frontal lobe dysfunction. This biology, however, has shown more change than his base IQ. These problems appear to respond to training, practice, medication, and time. They are problems that can be addressed.
So it is, at the moment, that I expect to explain his disabilities this way:
It is hard for you to work on things you don't enjoy. We and others can help you learn to do that. When you are able to work hard on things that are tiring and bothersome, you will be able to do many things. If you want to do an online High School degree then you could do that too.