FYI: (I checked with the PAGE legal team)
The TKES evaluation system CAN be used for your evaluation - even if you are being (completely) evaluated in an out-of-field area. So, if you're a chorus teacher and you have to teach drama, but don't have the ELA certificate yet, your annual TKES evaluation can be in your drama class; they don't have to visit your chorus classes at all. Same if you're a band director teaching a writing class. Essentially, GA law requires that teachers be evaluated through TKES no matter what they're teaching, even if they're required, and don't have a choice, to teach out of field.
Immediately I think about Standard 1: Professional Knowledge. That could be a real problem if mishandled by an administrator. I had an assistant principal say once about TKES, "You could bludgeon someone with this thing if you wanted to..." I agree more now than I did then.
