Sarah Forsyth, who taught the third in the line to the throne at the elite Eton College, told an employment tribunal she wrote virtually all the text for one of the prince’s key art projects.
Ms Forsyth, who is claiming unfair dismissal from the 650-year-old school which charges fees in excess of ₤22,000 (A$54,000) a year, also said she secretly recorded the prince thanking her for cheating on his behalf.
When her case originally began in October, Ms Forsyth alleged she had been ordered by senior staff to help him pass his art exam.
At the time, the art teacher considered her behavior to be “unethical and probably constituted to cheating”.
“I assumed I had been asked to do this because Prince Harry was a weak student,” she said in a statement, adding teachers at Eton had been “desperate” to find ways to award the young royal marks.
“However, I did not think I could tell anyone else about the incident without fear of victimisation and was not aware that statutory protection against such victimisation existed.”
“I have recently seen for the first time extracts of the written material which was submitted on Prince Harry’s behalf and can confirm that it was nearly all written by me.”
On Sunday the 20-year-old royal began training to become a British Army officer at the exclusive Sandhurst military academy.
His place at Sandhurst was dependent on him obtaining minimum examination results.
The prince just qualified with a B grade in art and a D in geography in his final school exams.
Ms Forsyth also added to an earlier statement, claiming the head of Eton’s art department would sometimes paint work for pupils as he talked to them to them about betting or soccer.
He also completed one of Harry’s examination pieces in the prince’s absence, she claimed.
Ms Forsyth, whose contract with Eton was not renewed during the summer of 2003, also claims she wrote the text to an art project handed in by the prince the previous year.
She said she has a secret recording of a conversation with the prince where he thanks her for writing “about a sentence” of his project.
Eton has denied the allegations, and insisted Ms Forsyth left the school simply because her teaching was not good enough.
The employment tribunal is scheduled to last two weeks.
The British royal family has dismissed the allegation, describing it as “incredibly unfair” on Harry and saying the recording on the tape was unclear.