What grade would this guitar piece be?

Man, I really liked it too. And, I can see you are enjoying what you are doing, and appreciate something as such a (more) classical approach. Even, famenco. Which is impressive, and great exercise to achieve.

Good for you. Always, beautiful scales to look forward to. Very important to be a well rounded player. Try everything (music styles) you can get your hands to work with, when it comes to the world of music. Important no matter what is in your hands (guitar instrument styles) and what they can give back in return.

But as for a grade scale, it has to be shown to your instructor according to what it could be rated as.

If you were my student, and know just how long you've been a player... at least a fat 'B'. Or, from 1 to 10... a 6 or 7. To keep you modest.

Being fair and just wanting to hear, and see, of what more you can come up with.

You've learned to appreciate as well, what makes for a good background to fit your playing style(s).

Smart cookie.