Two student named Burt were at the school for both sessions of 1810, Maria and William Burt. Maria stayed longer, through the end of 1814, one of the school's longest-running students. They were probably local kids--most boy students were--and the adult name attached to the account was William Burt.
William Burt appears throughout the school's ledger during Maria's school years, including a notation in February 1814 that she was taking music lessons as an add-on to her tuition. Oddly, for local students who stayed a while, there's very little else about the Burt children in the surviving Mordecai correspondence.
There were a lot of Burts in the vicinity of the Warrenton, and a lot of them were named William, so this took a little detangling, but.... This William Burt of Halifax NC married Martha Elizabeth Eelbank Bond (d. c. 1814), in 1797, and they had children William S. Burt, Harriet Burt (Mrs. Richard Eppes), and Maria Louisa Burt, according to various wills. Maria Louisa Burt married Henry Garrett before 1823. Her brother William became a doctor, married Priscilla M. Williams, and moved to Tennessee in 1833. (There was Mordecai student named Priscilla Williamson--hmmmm. I know from my own patronym that people add/subtract the "son" from such names very casually, maybe especially in the South, so that could be the same person.)
However! A different William Burt (1782-1848), also local, married another Mordecai student, Susan Sims, in 1812. He'd be too old to be a student at the school, but I mention him to illustrate the trickiness of all this. It'll be a while before Priscilla Williams or Susan Sims get their own entries at this blog, but when they do I'll link back to this.