There's no concrete evidence within the context of the scene that this is 100% confirmed to be Thomas Jefferson, but Jefferson is considered to be the primary author of the Declaration of Independence, so it seems only fair that he gets to be the one who reads it out.

Furthermore, this Simpsonified version somewhat resembles portraits of the man, so I'd say it was most likely their intention.

Most of my Jefferson knowledge comes from Hamilton, and this guy looks NOTHING like Daveed Diggs. I'd usually do a little more research on a historical figure like this, but as many of you know I'm British and the American revolution is obviously still a sore point for many of us.
Jefferson has appeared a few times in The Simpsons, although many of them are simply the appearance of Mount Rushmore. It seems there are three slightly more significant appearances after this: firstly, as the statue Lisa asks for advice in season 3's "Mr. Lisa Goes to Washington"

As a Quimby-fied version in season 15's "Margical History Tour"

And as an animatronic in season 30's "'Tis The 30th Season"

My heart says to me that these all qualify as distinct and separate versions of Jefferson (they even all have quite different basic designs), so look forward to seeing them all again when we get to them! The animatronic doesn't even speak, but by the time we get to season 30 I'll make sure to draw him specifically. Remind me, in the year 3742.
Now, scroll back up to the image of him from "Bart Gets An F". Did you notice that some of the other figures in Bart's perception of this scene resemble the train passengers from his other study session in "Bart The Genius"? The big noses and high up eyes, it looks like this slightly offbeat style was reserved for Bart's imagination, at least initially. I just found that interesting! I cannot remember when Bart next has an imaginary scene to play in, but we'll keep an eye out for these big nosed freaks.
This post is part of my "Every Simpsons Character Ever" series. For a list of my rules in this project, click here.