I don't think it would. My wife is a teacher and her contract states she is only paid for teaching time and school mandated events like staff meetings or training. Any kind of of time spent outside of school preparing lessons or grading isn't paid time. One of the tactics teachers use leading up to a strike is to only work contract hours and have everything else fall behind to have parents put pressure on administration.
Sounds like a good solution. Don't grade papers if there's not enough time to grade them during paid hours. Especially don't grade the standardized tests that the schools are so crazy about.
2x minimum wage for a 40 hour work week is the salary threshold. If you make less your employer is breaking the law. In California the salary threshold is currently $64,480.
Imagine being told that you have to work for free because they deem you worked too many hours in a world where you can hardly make enough to pay for rent let alone buy a house.