A Brooklyn high school science teacher took a student to a sex club, demanded underage students have sex with each other and sexually assaulted an 18-year-old teen, prosecutors said Tuesday.

Sean Shaynak, a Brooklyn Technical High School teacher, was arrested last month and accused of sending a sexually explicit photo to a student. He pleaded not guilty to those charges.

But as investigators reviewed evidence in the case, including hundreds of photographs and videos, they determined that he had also victimized six other girls ranging in age from 13 to 19, Brooklyn prosecutors said.

He was charged in a new 36-count indictment Tuesday. He now faces charges including kidnapping, criminal sexual act, obscenity and forcible touching. He is also accused of taking a 15-year-old girl to a nude beach, sending photos of his genitalia to four students, inappropriately touching and kissing others and giving alcohol and cigarettes to minors.

Shaynak, who pleaded not guilty, could go to prison for 25 years if convicted on the top charge alone. The judge set bail at $750,000 bond or $500,000 cash, prosecutors said.

Kimberly Summers, an attorney for Shaynak, declined to comment.

The Department of Education had pulled Shaynak from his teaching duties following initial arrest and was in a rubber room. On Tuesday, a spokeswoman for the DOE said he would no longer have contact with students.

"These alleged actions are completely unacceptable, and have no place in, or outside of, our schools," said DOE spokeswoman Devora Kaye.

Shaynak continues to collect an annual salary of $52,744.