Well, no. But it made such a good story....maybe that's why we all heard it was true!
The National First Ladies' Library writes:
It is not true, as so often stated, that Eliza Johnson taught her husband how to read and write, but it is true that she helped him refine his rough edges.
Her White House biography tells us some more:
Fortunately she [Mrs. Johnson] had received a good basic education that she was delighted to share with her new husband. He already knew his letters and could read a bit, so she taught him writing and arithmetic.
The NFLL shares with us what they see as her legacy:
Eliza Johnson’s life in the White House was only a continuation of the pattern she followed throughout her life – home and family first and foremost. At no point did she involve herself in her husband’s career, not even at the start. She had a calming influence on her easily angered husband and in this way, exercised a real power. She showed no interest in expanding her role in his life and had no interest in the world of politics. Eliza Johnson was a very conventional woman, who turned over her duties as First Lady to her very capable daughters. Her refusal to fulfill her duties was due in part to due health, but also due to the public criticism of Mary Lincoln during her four years in the White House.
Go spend some time and learn about this fascinating First Lady! And go and share your new information to help replace with the myths with the truth about Eliza Johnson!