I go to a 5A school in region 7, and it's not very hard to switch from 5A to 6A when you're registering. Your band director should have forms that kids will fill out, and I don't think you have to pay extra or anything like that. It's up to you to decide whether to go 5A or 6A based on your playing ability. Your private lessons teacher can help with that; you have a while to decide which track to go. It's normally in late fall when you'll get the form, but still before Phase 1 (I'm pretty sure). In region 7, there are only 2 6A schools and a lot more 5A schools (like 5+, I think?), so that might be why your band director said it's a bit easier to make area on 6A, since they take more kids to area. I actually don't know that region 5/Haltom is in our area, since we go to Midland to compete, but I could be wrong. But your best resource is your band directors and private lessons teacher. They can help you out the most.