A controversial principal has been nailed again — this time for giving a bad review to a whistleblower.

Greta Hawkins of PS 90 flunked teacher Vicky ­Giasemis last school year because the principal “bore significant animus” toward the veteran instructor, an arbitrator ruled — ordering her to submit a new evaluation.

Hawkins had it in for Giasemis, a chapter leader for the teachers union who had filed a successful grievance for 13 teachers charging Hawkins with harassment in 2013. Hawkins saved a union newspaper calling her a bully as “a daily reminder of who she held responsible,” arbitrator Marlene Gold found.

Giasemis earned “effective” ratings based on how her third-graders performed on state and city tests, but Hawkins rated her “ineffective” while not performing extensive classroom observations, Gold said.

Hawkins, who had previously banned kids from singing “God Bless the U.S.A.” at graduation, will not be disciplined, a DOE spokesperson said.