A city public-school principal’s reputed idea of a good time in Las Vegas will cost the city $300,000.

The cash settlement ends a sexual-harassment suit filed by Frank Farino, an assistant principal at PS 43Q in Far Rockaway, Queens, who said his ex-boss hit on him during a 2009 Sin City junket.

Before the trip, Farino claimed that now-retired principal John Quattrocchi flirted with him and gave him a birthday card depicting “a naked man.”

The uncomfortable situation got worse in Vegas, where Quattrocchi demanded that Farino accompany him to gay nightclubs, kissed Farino on the lips, and later forcibly fondled Farino in a hotel room, the suit claimed.

When Farino rebuffed his boss, professional retaliation followed, the suit said.

Quattrocchi’s attorney, Paul Montuori, called the accusations “absolutely, patently false.” A city spokeswoman said the settlement “was in the Department of Education’s best interest.”

But Joshua Friedman, Farino’s attorney, said the case reveals an ongoing risk to students and workers in city schools.