A Brooklyn teacher claims he blew the whistle on a cheating scandal, and lost his shot at a full-time job.

Robert Rodriguez was hired as a substitute in February 2009 at Fort Hamilton HS and eventually given a permanent assignment as a social-studies teacher there until, he claims, he reported “open cheating,” according to a Manhattan federal-court lawsuit he filed.

During the 2010-2011 school year, Rodriguez saw Assistant Principal Gregory Abood allegedly “providing students with answers” during Regents exams, he claims in court papers.

When Abood realized Rodriguez had sounded the alarm about the alleged cheating, he refused to give the whistleblower a teaching job that fall, Rodriguez charges.

The city Law Department is reviewing the lawsuit, a spokeswoman said.