Our high school is considering that as well. Up until now it has been an informal program for seniors who sign up for “office” but negotiate an agreement with a particular teacher to do the work for them. “Office” is a graded course, but as long as you show up and do your job cheerfully and fairly accurately, you always get an A.
I was going to add that my sister, who teaches at a junior college, also always seems to tote work around to grade during holidays and on weekends. It is part of the job of teaching, but can be lessened if you do what @jazzjeppe says, and think about the types of assignments and tests you need the students to do.