AIBU to think this teacher was victim blaming?

[Natsku]

There was an incident in DD's class yesterday, the art teacher left the class for a moment to fetch something from another classroom. During that time, one boy (call him boy A) hit another boy (boy B) very hard. Boy B ran out of the classroom crying and boy A stormed out just as the teacher was returning. The teacher asked the rest of the class what had happened, now both boys were gone, and then said to the class that they must not annoy boy A because he reacts easily like this.
She hadn't been told if there was any argument or provocation, she emailed the parents to say that she was still waiting to find out the details, so I feel like she jumped to the conclusion that boy B must have annoyed boy A and caused himself to be hit.
The children are 10/11 years old. According to DD boy A often does things like this, though its the first time a teacher has ever told us.

Which country is this?

The teacher is 100% responsible for supervision during class contact hours and has a duty of care to NEVER leave the class unattended. This would be a disciplinary procedure where I work.

Also a teacher must protect the child's right to privacy and GDPR, it's unacceptable to divulge this kind of information. I would be complaining on these grounds.

Finland.

If she was out of the class for that long, has told the parents in the email that the class shouldn't be left alone, but she had no choice, and has emailed a lot of details I'd be assuming she wants a lot of people to complain...

Is there a staff shortage in the school? I'd wonder if she'sbeing split between classes, has raised concerns about it and been ignored.

I wouldn't have thought there was a staffing issue, usually the class has their teacher and a teaching assistant and its a very small class, but it sounds like the teaching assistant wasn't there so maybe she doesn't go to the art lessons so less support for the teacher. But being split between classes seems unlikely.

Well something must have happened, why else would the child thump a classmate hard and then run out of the class? I mean obviously he shouldn’t have responded in that way, but I would give the teacher some credit for knowing the characters involved. She has been spending every day a week with these children since September! She knows the children, what winds them up, how they respond, and the relationship dynamics. I bet she has a pretty shrewd idea of the sort of thing that goes on when her back is turned.

She's the art teacher not their class teacher, only sees them once a week. Of course I'm sure she knows the class fairly well by now but not on the same level as a teacher that sees them every day.