I agree with what others have said so far. I think that most scholars would consider Luther the starter.
Perhaps your teacher does not consider Lutheranism truly “Protestant.” Martin Luther held onto many of the beliefs of the Catholic Church, especially the belief that the Eucharist is Truly Christ **(once it is consumed = consubstantiation). **Theoretically, the religion of Martin Luther could be called “Catholic Lite.”
But Calvin more or less totally disgarded Catholicism. He denied utterly the True Presence of Jesus in Holy Communion, as well as many other Catholic doctrines, and many of the doctrines he watered down (e.g., baptism–no pun intended!).
Also, Calvin was the FIRST theologian to WRITE a systematic theology of the new religion, Institutes, so perhaps your teacher thinks that it was only when Protestantism was actually WRITTEN DOWN that it actually became a real religion instead of just a revolt of one disgruntled man . Perhaps your teacher believes that if Calvin hadn’t written Institutes, the whole Protestant revolt would have died out within a few generations. Hmmm.
My daughter graduated from Calvin College, BTW! You might want to contact them for (name removed by moderator)ut–I think that some of their faculty would be interested in writing you back. I wrote to their Dutch Department for a translation of a phrase in one of my novels, and two professors wrote me back.