It's up to you whether it's worth your time and effort. At $50k X 25% X 2.31% = $289.
You'll have to go before the Board of Equalization and present your case. They don't have forms on their site, but I'm sure you'll have to present details of sales transactions showing recent non-foreclosure sales prices for comps of your house. You'll have to include adjustments for bathrooms, bedrooms, square footage, lot size, age of house, etc.
Williamson County, TN - Official Site - Board of Equalization
If that's worth $289 annually to you, go for it.