A.N.
My son was in the same boat last year (Sept 4 birthday), except we don't have TK. He did a second year of preschool last year (super bored though), and luckily got into a very challenging school through the lottery, the only public school that is full day in my area. He would be bored out of his mind if he had to go to normal half day kindergarten this year as an almost 6 year old, but at his kindergarten assessment at the beginning of the summer, his school said he should work on 1st grade workbooks over the summer to be ready for kindergarten, so I know he will be challenged if they are at that level. I think his kindergarten experience this year will be perfect for him, but only because of the specific school he is going to. If the school you want to go in is a better school and will challenge her more overall, it isn't a bad idea to put her in TK and go to a better kindergarten next year that will still challenge her.