I guess it was just a matter of time.

I received an email from one of DS teachers that stated:
"Over the course of our time together, I have watched [DS] throw out seemingly benign comments that have put the people around him on the defensive. This behavior has made the atmosphere of the class edgy. When talking with [DS] about it I said that it felt like very aggressive passive aggressive behavior. I asked him if he knew the behavior that I was referring to and he confirmed that he did."
I responded and told her that even when DS states that he understands, he probably doesn't, and asking him for a specific example would probably confirm this.
DS came home from school and I asked him about it. He said he didn't know what she meant but nodded and agreed (he thinks this is the expectation). He said she told him his "words have knives" but he, in a moment of unusual insight (yay!), said he thinks it's because of his tone of voice and his facial expression, both of which stay the same all the time and have an irritated, annoyed quality.
I asked for an example and the only one he could come up with was that he told a classmate it would be faster to learn to use the shift key than using caps lock when keyboarding.
I'm not sure if he's right about his example, but if he is, I understand why teacher said "benign" since this is pretty benign, but could sound snotty if said in a particular way.
He was also pretty confused by her analogy (knives) and I kind of laughed a little since that is about the worst way possible to communicate with a literal kid with autism.
He can't help this, but he wants to do better.
I asked the teacher if she's willing to work out a discrete cue for letting him know when he sounds unpleasant--we'll see.
In the mean time, any ideas about how to help at home? I decided to delay the SLP eval because he can't miss any more class right now. He's going to work with CBT therapist for the rest of the semester on EF issues and anxiety and then next semester, we'll do SLP therapy.
Since the school won't do anything to help him, we are kind of piece-mealing.
Thanks in advance for any advice.