This story happened a long, long time ago, almost 10 years now. It's still exactly what I think of when people tell me about their kid who will "never" self advocate.
I worked for a few years with a boy who we will call C. C was about 9 when I met him. He was nonverbal, really hated typing on the computer, knew a few signs, and had a PECS book. He had experienced many years of ABA therapy, which is very much therapist directed, and he was growing increasingly frustrated with how things in his life were going. His frustration was pretty clear-he was angry a lot of the time and he was lashing out physically when a lot of demands (or unpleasant demands) were made. His PECS book often didn't have what he wanted to communicate in it, so that added further to his communication challenges. What he was left with was behavior as communication.
I'm pretty sure C's parents weren't exactly looking for self-advocacy teaching, at least not what I do. They had the whole "autism as tragedy" thing going on, were into quackery, kind of seemed to resent C for existing (ok, so very much resented C for existing) and wanted compliance and normalcy, not what I was offering. But C and I hit it off right away & I wasn't completely horrified by his expression of his anger. I avoided getting hit, obviously, but I wasn't going to restrain him or, nearly as bad, throw more and more demands in his face when he was upset. That's silly. It does not work. Typicality is not a realistic goal, but being able to express wants and needs is, and it was quite likely that C could learn a more expedient way to make his wishes known.
When I started working with C, I had a rule for his ABA therapists and parents: if C made clear a want or a need, he gets it. If he indicates that he doesn't want to do same with same or whatever, he doesn't do same with same. If he indicates that he is not ready to leave an activity, he doesn't have to leave yet. He needed to learn that he has some agency after so many years of following other people's agendas.
What's the first thing little kids tend to learn to take power over their lives in small ways? The word "no", right? I wanted C to learn that he could ask for things and get them, and that he could say he didn't want to do things and get that. A lot of our time was spent playing and him indicating he wanted or didn't want things, and me putting into words "No, don't take your block? Alright!" or whatever when he indicated in any way that he didn't like what I was about to do or did like or want something. Showing him that adults do take his wishes into account.
Then I took C swimming one day. This was something his ABA therapists didn't like to do very much because apparently it's a battle to get him out of the pool, he liked swimming in the deep end even though he wasn't an awesome swimmer & keeping him in the shallow end could be meltdown inducing-he could swim, but needed an adult right there. Not a battle I wanted to fight, but I'm not a fan of the Adult As God paradigm. I liked swimming and I liked C, so it was a good time.
We did some laps, we (well, C) splashed around in the shallow end, and 15 minutes before we actually had to leave I asked C if he was ready to get out.
Clear as day, emphatic, and with feeling.
Yeah, we didn't get out of the pool for another 10 minutes. C indicated no, he was enjoying himself, he did not want to leave. And he did it in a way that no one could deny-no is an important concept in making one's needs known, and everyone knows what it means.
He used the word NO a whole lot-they made him do a lot of inane things (touch nose? Really???) and he didn't want to. I don't blame him; touch nose is not exactly a meaningful activity. He started indicating preferred activities & even started helping make a schedule of stuff he'd do during his sessions (or what toys we'd play with & such...interactive toys for demonstrating "I don't want to" or "don't do that" are pretty great).
Then he stopped & started biting again. Being bitten hurts. Biting wasn't getting him what he wanted. "What. Did. You. DO?" was my question to the ABA people.
"Oh, he didn't want to do (some meaningless task) and I hand over handed it."
"...what the hell is wrong with you?" (insert about 15 minutes of full volume yelling about how it was his body and he had a right to not be touched and he had a right to determine his activities, and she owed him one hell of an apology, and he was going to get that apology. Where C could hear it. And where C's parents could hear it, because they were in the same county).
She thought I was kidding. I wasn't. She quit shortly after-apparently apologizing to a just turned 10 year old was beneath her, or to an autistic kid, or being told to by an autistic adult, I dunno.
And C started saying NO! again. Then we started fixing his book & set up a dynavox, but that's a whole other story....