Evelyn M. Wood says Joseph might have been taught his letters in around 1810.
Evelyn M. Wood Lovejoy, History of Royalton, Vermont, with family genealogies, 1769-1911 (Burlington, Vermont: 1911), 646
Father Smith taught common school for several winters while the Smiths lived in the Prophet's birthplace. But young Joseph was not ready for regular instruction until after his family had moved to neighboring Royalton Township, where Joseph Smith Sr. appears on the tax records from 1809 to 1811. A granddaughter of Royalton deacon Jonathan Kinney said he "oft repeated" that "I taught Joseph Smith, the Mormon prophet, his letters while teaching school upon Dewey Hill about the year 1810-15."