A teacher is under investigation in The Bronx and Staten Island amid accusations she had a long sexual relationship with a mentally ill 16-year-old student at a school for children with special needs.

Sandy Carazas-Pinez, 33, a former NYC  biology teacher who is married with three children, had sex with the teen in her car at least a dozen times, and sent him nude and erotic poses among scores of inappropriate texts, according to allegations by the boy’s mom and documents obtained by The Post.

Police and district attorney investigators compiled reams of texts sent at all hours between the teacher and the teen, who attended the Biondi School in Yonkers at the city Department of Education’s expense. It is run by the nonprofit Rising Ground, which terminated the teacher this month.

“I know for me it isn’t going to be easy, I will miss your kisses, hugs and everything,” Casarez-Pinez allegedly wrote this year in a discussion of whether she and the boy should “end it,” according to  texts under review by law enforcement agencies.

In January, she allegedly angrily responded to messages from the teen pleading for a response, telling him: “Throughout the whole vacation you have shut me out and the only time you would hit me up was when you wanted to .   . .  tell me that you are crushing on other teachers . . . I am not a piece of ass with no feelings.”

Reached by phone Friday, Casarez-Pinez denied having sex with the student: “I didn’t even know there were these allegations,” she said, adding that investigators have not contacted her. “He would tell me he loved me and I would just reciprocate.”

She said he got in her car once because “he asked me for a ride and it was snowing that day.”

Asked about the nude photos texted to the boy, she said, “He had the passcode to my phone.”

On an earlier call, Casarez-Pinez’s husband angrily confronted her after asking a reporter about the allegations: “You told me you quit, Sandy,” he said. “You’re done, Sandy, if this is true. . . . You’re f–king done, pack your stuff and leave.”

Her husband called The Post reporter Saturday to say he’d kicked her out and she was staying with her parents on Staten Island.

In other texts under scrutiny by investigators, the teacher apparently wrote: “I do miss your touch and kisses not going to lie. . . . I sound like a pervert.”

The mother said her son told investigators the two “fondled” each other sexually in class.
Casarez-Pinez also asked the student to lie to cover her tracks, the texts indicate.

Other evidence includes a recorded phone conversation, obtained by The Post, in which the boy asked Casarez-Pinez why she was “pulled out” of the school: “Did they see us having sex, or did they see me getting in the car? They didn’t see us having sex, so what’s the issue? . . . We hid from the cameras, though, right?”

She replied, “They’re saying we were too close … that it was pretty much like us being in a relationship. And that’s, like, against everything. One, because you’re underage, and two, because I’m your teacher.”

The teen suffers from a combination of schizophrenia and mood disorder, his mother said.

“We are upset, shocked, and appalled by the behavior of a former teacher who betrayed the values of the school by engaging in an inappropriate relationship with a student,” Rising Ground said in a statement.

The boy’s mother — whose name The Post is withholding to protect her son’s privacy — is livid that authorities have not arrested the teacher more than two weeks after the teen gave a lengthy interview March 7 to NYPD special-victim detectives in Staten Island, where the family lives.

“If my son was not an African-American boy, and the genders were reversed, you know the teacher would already be in handcuffs,” she said.

She quoted one officer as crassly joking, “Where were those teachers when I was in high school?”

“It’s the rape of a child with a mental illness,” she said. “As a society, we have to prioritize the safety of children who are mentally ill and boys who are sexually assaulted.”

Before joining the Biondi School, Casarez-Pinez taught at PS/MS 007 in Harlem, and PS/IS 218 in The Bronx. DOE officials had no comment.