Here's how the rabbi responded: (my translation)
Per the question you asked me regarding what you had heard about Yeshivos permitting their students to steal the answers to the questions for the terminal test administered by the state (regents [sic]) so that they receive their diplomas in good standing, this is forbidden, not just because it is the law of the land [dina d'malchusa dina] but also by Torah law [din Torah]
-- Igros Moshes Choshen Mishpat 2:30
I'm happy to see that Rav Moshe's prohibition was unequivocal, however, I'm rather worried about the man who asked the question. What was his assumption? That stealing might be ok?
Where did he go to school?