writing prompts

I have been instructed to give a writing prompt to each of my classes, and this once a month from October to April. This method of reinforcing writing skills, I believe, is sorely ineffective. If the point is to help students learn to write more efficiently, then we should instruct them on how to write, give them a chance to apply it, and then give them adequate feedback that would help them on future performance. This is not how our district has mandated this "writing across the curriculum" plan. They are having us give the students writing assignments (once a month, as stated above), and keep them, not giving the students any feedback. Not only do the students not receive feedback from the teacher, but the district is asking that teachers, who have not been instructed in the ways of grading English, now be required to grade essays based on the "6 Traits of Writing" rubric. I was trained for elementary education, so I am familiar with and could grade with the "6 Traits of Writing," but most of the math department (let alone other non-English deptments) have not been trained in anything but the subject that they teach. I chose to teach Mathematics and not English on purpose: I didn't want to grade the writing! Now, as a math teacher, the district wants me to grade 140 papers on a writing rubric. If the district wants stronger writers, they should up the instruction and feedback on the students' writing, not give them more work without any instruction or feedback for progress. What's next, "math across the curriculum"? Let's see what kind of non-math teacher feedback there will be while trying to grade quadractic equation problems. That'll be the day.