I am a teacher/coach in a Mississippi Public School District. My job description says I am a 10, 11, or 12 month employee but I have only been paid for 9 months for the previous 8 years. I am getting ready to ask for my back pay. How many years back can I ask for by law.

8 years is way too long under the state DOL guidelines. It's normally 2 or 3 years. However, are you sure it was just the way it was calculated? Did you receive your full annual salary over those 9 months? If you have an employment contract, then you could go back further. But if there is a violation of law or contract here, I don't know why you waited so long.