I wish high school teachers would take note of this. My kid goes to an accelerated program high school in Toronto and she is so swamped with homework and tests, she hardly gets any sleep on weeknights and on some weekends too.
You can take them out of the accelerated/gifted program and put them back on the "normal" university track in high school.
The big risk is that it will cause your kid to get alienated socially among both the "normal" and the "gifted" kids, so make sure that your kid is involved in the decision-making process.
If your kid has an IEP, you can also talk to the teacher to get accommodations. For example, maybe your kid could quietly work on their homework during their school day, instead of being forced to pay attention to the teacher's lecture.
You can also just tell the kid that they can decide how much homework they want to complete. In high school and university, any un-completed work just gets recorded as a zero; if the kid is already getting 80s and 90s then a few missed or half-complete assignment questions shouldn't materially affect their final grade (provided they understand enough of the main concepts to complete major tests/projects/exams). Having a strategy for deciding what work is safest to drop/defer when you're overwhelmed is a useful skill both in upper education and in the workplace.
Source: Went to a high school in York Region.
https://www.psychologytoday.com/us/blog/dream-catcher/201112...