SEX-PRED PRINCIPAL GUILTY
    An Upper East Side private-school head mistress faces up to 18 years in prison after her conviction yesterday for sexually preying on a young male student.

    After deliberating for six days, a Manhattan Supreme Court jury found Lina Sinha, 40 - a respected educator with two master's degrees from Columbia - guilty of two counts of oral sodomy and one count of felony witness bribing stemming from her attempts to cover up her crimes.

    The dark-haired beauty, a one-time director of the Montessori School of New York on East 55th Street, was being held last night after the trial judge set her bail at $3.5 million.

    The victim was only 13 when the pe dophile principal - at 29, more than twice his age - sat him on a white porcelain sink in a rear classroom of the school and gave him his first oral sex. "She told me that she loved me and that one day we were going to get mar ried," the victim - now a cop, 24, in Queens - told jurors.

    He had yet to shave. He only stood as high as her chest. Still, Sinha promised him children - the boy to be named after him.

    She taught him to reach her bedroom above the school by sneaking past the security cameras installed by her parents, who owned the institution. She stocked her room with video games and kept him there weekends at a time.

    The cop compellingly testified to these early trysts, which eventually evolved into a twisted, nine-year relationship with Sinha.

    Sinha was only unmasked after she waged a virulent campaign of false rape and assault accusations - including in-person interviews with cops and hysterical calls to 911 - against the probationary officer upon their 2005 breakup.