I don't believe, as an ex-English teacher, that any teacher thinks a student is 'acing' their essay if that's not shown in their other writing.
Little Johnny, with his poor spelling and grammar, does not suddenly turn in an excellent paper with exemplary grammar, spelling and punctuation. So unless they teach computers how to screw up in the exactly the same way that Johnny does every time he writes a sentence, any teacher worth his salt is going to know it's not his work.
As for those with excellent writing skills, well, they have less need to cheat but even they would be sussed out with in class essays and assignments.
> unless they teach computers how to screw up in the exactly the same way that Johnny does every time he writes a sentence
You can ask an image generator for something like "Barack Obama painted by Picasso" and get a passable result, so it's probably possible to augment a writing model to mimic the style of Johnny's past essays.
Little Johnny, with his poor spelling and grammar, does not suddenly turn in an excellent paper with exemplary grammar, spelling and punctuation. So unless they teach computers how to screw up in the exactly the same way that Johnny does every time he writes a sentence, any teacher worth his salt is going to know it's not his work.
As for those with excellent writing skills, well, they have less need to cheat but even they would be sussed out with in class essays and assignments.