I'm from Texas, too. You can apply to the board as soon as you want!
What determines your ability to test is how quick the BON sends you the ATT letter after graduation. Mine took two and a half weeks, and even then there wasn't anything available as far as test dates until a couple weeks after that!
This is what I did, if I remember right... the BON gives pretty good directions here
for initial licensure.
with Pearson Vue a few weeks after that (the BON says two weeks before graduation, but you can do it earlier.
3. Graduate and wait for your ATT!
4. As soon as you get your ATT, schedule
your testing appointment.
Good luck! Have a great last semester, and happy job hunting.