States do have varying requirements but the variation usually comes from the exams, not the content area (30 credits) or the pedagogy requirement (education courses and student teaching). I have a friend who did her MAT in one state but has easily gotten certified in 3 additional states. She only had to pay for new certification and take the state exams and any other requirements (for example, a state may require a health and hygeine exam). If you at all want to teach public school, I would go for the MAT. Just make sure you end up with 30 Classics credits (between your BA and your MA) and you take a world language or Latin teaching methodology course. If you don't go the MAT route, and you do want to teach public school, where the money is usually better, you will have to hope the state has an alternate route program or you will have to go back to school to make up the required pedagogy coursework.