It always irritates me the way they seem to spend almost no time with Adam, then leave him to Willie and expect him to do what's right! When Barnabas spent a couple of minutes with him, giving him food and then left, he said, "I'll be back tomorrow, my first reaction was, what else does he have to do? One would certainly expect them to spend most of their time with him, working with him. And, again, what else do they have to do? (Julia never seems to go to Windcliff.)
However, apparently they ARE doing more teaching than we realize and we're just not seeing it. Barnabas asked how he learned about using a spoon and, later, the napkin and whether Julia had taught him. Barnabas told Julia that he had spent the day with him and then left to get him food. So, perhaps it wasn't just those couple of minutes. When Adam said, "music," again my initial reaction was to wonder how he had learned that word. Then Julia said something about him remembering her teaching it to him. So, perhaps they aren't as bad as we think.
(I'm not saying they're good, but not as bad as it would initially appear!)
I was also surprised at Barnabas preparing to return to Collinwood as Julia was treating Adam's shoulder. They know how he can react, especially to pain. She's treating a bullet wound. One could reasonably expect that she could happen to hurt him and immediately be subjected to an attack. But, as soon as he seems to be calmed down, Barnabas is ready to leave her alone with him!