Essays are written IN CLASS, until senior year. (Yet another anti-cheating issue.) He himself tells me that he is confused at what the teacher is looking for.
Sigh... I do understand the cheating issue, but you'd think that they could come up with new essay topics each year! My son, who is very literal, sometimes misses what they are looking for as well, and it's been extremely helpful to go over his essays with him. I think sometimes gifted kids see the world in a bit of a quirky way! I am sure that your son (and mine, I hope :)) will eventually get a better sense of what the average teacher is looking for, but it's frustrating that the students at your son's HS can't take home the tests/essays and spend a little time learning from them. For my son, the right answer was usually in his brain, but he didn't seem to always understand how to match up the correct information with what the teacher wanted, if that makes sense.
Good luck meeting with the teacher, whenever you do it. Don't be afraid to push back on her recommendation to drop him if you feel like he is in the right class!