One of my kid's teachers sent out a warning to students that all essays would be checked with AI detection software and the repercussions one would face if caught. A classmate did an AI check on the teacher's warning and it came back positive for having been AI-generated.
The default tone of ChatGPT and the default tone of school or academic writing (at all levels) are not exactly the same, but in the grand vector space of such things, they are awfully close to each other. And all the LLMs have presumably already been fed with an awful lot of this sort writing, too. It's not a surprise that a by-the-numbers report, either in high school or college, of the sort that generally ought to get a good grade because it is exactly what is being asked for, comes out with a high probability of having been generated by GPT-style technology. And I'm sure LLMs have been fed with a lot of syllabuses and other default teacher writing documents, and almost any short teacher-parent or teacher-student communication is not going to escape from same basin of writing attraction that the LLMs write in very easily.