[TN] District baited-and-switched my pay after approving me to teach summer school

Hello all, I have a weird situation involving my employer that I could use some guidance with. I am in Tennessee for reference.

I have been an Educational Assistant (EA) at an elementary school in my district for the last 6 years.

I just finished my teaching degree at an out-of-state online university and completed student teaching at this exact school, so my teaching license is currently processing and taking a bit longer than normal in-state licenses.

Back in April, I applied for a Summer Learning Camp (Basically summer school) teacher position within my district. In my initial email to the admin and the director, I was 100% transparent and said I likely wouldn't have my license in hand by the time summer school started, and asked if I could still teach. The director emailed me back and said that she would approve of this. I have explicit permission from her in writing from 2 months ago.

Fast forward to last week. I worked May 27-28 (mandatory setup days) and this week June 1-3. The entire time, I did 100% of the duties of a lead classroom teacher, including setting up the room, lesson planning, instructing, and contacting parents.

Just today the admin told me I'm not allowed to teach because I don't have my license yet. Because of this, they are retroactively cutting my pay for the days I already worked to an EA rate ($25/hr, half of the teacher rate). On top of that, they refuse to pay me money for the two setup days, saying I will only get "comp time."

Admin was useless to help me and instead tried turning things around on me and saying that I'm not qualified for the position and they have to cut my pay. They have zero care about this at all and basically acted like I have made a huge inconvenience for them.

I am completely devastated and furious. I was upfront from day one and have the screenshots to prove they approved me to teach without a license. I literally can't figure out why they decided to do this at the last minute and screw me over. I even asked admin on May 27th (the first startup day) to see if everything was still okay for me to teach and they said it would be completely fine.

My questions for you all:

1. Since I am resigning, "comp time" is useless to me. Can they legally refuse to pay me cash for those setup days I worked?
2. Can a district legally slash your pay retroactively for hours already worked under an agreed-upon role?

The admin of the summer school camp is besties with a few people in HR so I also don't feel good about what the outcome will be. I would appreciate any advice on this