Volume XV of Wisconsin Historical Collections contains a letter from an Augustus T. Ambler. The purpose of that letter was to report the death of the Stockbridge Mohican's missionary, Jesse Miner, to the philanthropical society that supported his work. Miner died in March of 1829.
In that same letter, Augustus T. Ambler reports that he had been teaching for three months and had also been sick for three weeks. Ambler adds that "Electa Quinney, a competent native teacher, will probably take charge of the school this summer."
And she did. Electa Quinney had taught for six years at New Stockbridge, New York and after arriving at Statesburg (which is now Kaukuana, Wisconsin), she taught the children of her people for one more term, in the summer of 1829.
I pieced these things together at about the same time that I got access to Electa Quinney's only known biography, an unpublished college term paper written by Annie Paprocki in 1999. Paprocki says the same thing: Augustus Ambler taught in the winter of 1828-1829 and Electa Quinney took over the teaching duties the next term, before being replaced by Jedidiah Stevens.
Here's a somewhat amusing sidenote:
Out of an understandable eagerness to point to positive role models (or to make money on the web), people need to be careful not to make false claims. I came across a webpage that even claims Electa Quinney was South Dakota's first schoolteacher. Correction: Electa Quinney never even lived in South Dakota. Also, there is no Kaukauna in South Dakata.
Anyway, to wrap it up, I think Annie Paprocki was right to conclude that Electa Quinney is still a good role model despite not having taught school in 1828. You don't have to be the first one to do something to be a good role model. Electa Quinney was a Christian schoolteacher, and later a wife and mother at a time and place where nothing came easy - especially not to Indians.