It was just past midnight last May when Marisa Cazanave poured her heart out in an e-mail and hit “send.”


“You make me unbelievably happy,” began the rambling love letter. But the Brooklyn Technical HS teacher’s confession was wracked with mixed emotions because the object of her affection was her student.


“I can’t say I’ll ever get past the fear of being discovered,” the married teacher, 33, told the boy. “But I can promise I will do my best to work on that.”


Cazanave’s alleged taboo affair is just the latest in a local and national educational epidemic. In New York City, the Special Commissioner of Investigation, Richard Condon, has fielded 995 complaints about “inappropriate relationships” between Department of Education employees and students since April 2009. SCI substantiated 145 of them, the agency revealed Friday.


The evolution in education technology is partly to blame.


Many of the SCI cases involved Internet or cellphone communication. In 2005, only about 20 percent of teenagers had cellphones, but today nearly 95 percent of US high schoolers carry one.


In the last decade, tools like online portals, school e-mail and messaging systems have emerged, making “it far too easy to slide down the slippery slope from empathetic teacher to sexual predator,” said Frederick Lane, a Brooklyn attorney and ­author of the book “Cybertraps for Educators.”


Lane estimates 70 percent of illicit student-teacher hookups are “accidental” and begin with an innocent exchange about homework that escalates to shared secrets, sexting and sex.


“There’s incessant communication going on and teachers can keep constant tabs on the victim,” said Terri Miller, president of Stop Educator Sexual Abuse Misconduct and Exploitation (S.E.S.A.M.E.), a national victim-rights group.


Many inappropriate exchanges occur late at night from bedroom to bedroom. “It evokes a more emotional and intimate reaction,” Lane said.


Phone records show Cazanave, who ran the choral program at the elite 5,500-student Brooklyn Tech, spoke with her smitten student 145 times between 10 p.m. and 2 a.m., according to an SCI report.


Casanave denied to The Post that she and the boy had sex.


Texting heated up a romance between International HS at Lafayette chemistry teacher Lindsay Dunaj, then 25, and 18-year-old student Dmitry Prokofyev in 2009. But Dunaj broke his heart at the senior prom when she drunkenly kissed and slow-danced with another student.


“I’m sorry that I hurt you — obviously I never wanted to do that,” Dunaj apologized in an e-mail to Prokofyev. “This is something that has made me realize that I need to be more clear about my boundaries with students.”


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Jay Travis, then 34, an English teacher at Brooklyn Studio Secondary School, started flirting with a student over text and e-mail. After several months, the relationship turned sexual. They exchanged 2,382 messages and phone calls during their affair, the SCI found.


“My heart was invested in it and it was the most conflicted I ever felt in my life,” Travis wrote to the teen in an e-mail on Sept. 6 2012, after the student broke off the affair. “The circumstances of how and when and who we were when we met were just not fair.”


Most errant educators are one-time offenders.


Lane estimates 70 percent of illicit student-teacher hookups are “accidental” and begin with an innocent exchange about homework that escalates to shared secrets, sexting and sex.


But some 30 percent of student-abuse cases involve predators who use technology to groom students for their physical pleasure, Lane said.


“The sad and unavoidable truth is that there is some small percentage of educators who actively seek to abuse the children they teach,” Lane wrote in his book “Cybertraps for Educators.”


Ian Millman, a teacher at the World Journalism Preparatory School in Queens, began a relationship with a sophomore who came to the 40-year-old for help with depression because he was known for talking to kids about their personal problems, the SCI reported.


After exchanging phone numbers, they shared 25,000 texts per month and began having sex, SCI reported.


When the teen got pregnant, he forced her to get an abortion, and refused to leave his wife despite the girl’s pleas, SCI said.


When SCI first got wind of the relationship, the teen lied to protect the teacher. But her mother found damning e-mails.


“You honestly feel like you loved this person. They’ve groomed you into thinking this is love,” said Michelle Stolleis Forbes, 45, who was sexually abused by her teacher in Illinois for eight years starting in 1986.


Forbes was 15 when her teacher asked her to be his “secretary” and began molesting her. A few months later, the teacher was driving Forbes in a car when he pulled over and “taught me how to perform oral sex,” she said.


“There were times that my mind would say ‘well, this isn’t right,’ but he also made me feel special.”


One of New York City’s most notorious teachers, Sean Shaynak, 46, was known among Brooklyn Tech students as “Shay-Shay.”


“He acted like a teenager himself and hit it off with everybody,” one of seven girls he was convicted of sexually abusing told The Post. “He would talk about his own life and struggles, and be a friend.”


But Shaynak, who taught math and aeronautics, allegedly bombarded his pets with sexts and lewd photos of his genitals on Snapchat.


“I was in the middle of cleaning my room” when Shaynak sent a shot of his erect penis sticking out of his pants, she said. “I had received so many of those it wasn’t a big deal.”


When Shaynak persuaded her to visit his apartment to “help hang paintings,” he forced vodka down her throat and physically assaulted her. On another outing “to run errands,” he took her to clothing-optional Gunnison Beach in New Jersey, and stripped naked. No one could reach her because Shaynak told her to turn off her cellphone.


“He told me that part of ­growing up was learning to lie to your parents,” she said.


Experts call for stricter rules on teachers communicating with students after hours.


In New York City, teachers are forbidden to talk to students through their personal social media sites, but communication on “professional” profiles is fair game. Some districts elsewhere go even further, prohibiting teachers from responding to students’ private e-mail addresses.


When SCI first got wind of the relationship, the teen lied to protect the teacher. But her mother found damning e-mails


“Setting up class pages should also be banned. It’s just risky behavior,” said Miller of S.E.S.A.M.E.


Lane believes teachers should not respond to students outside school except in emergencies.


“Traditional boundaries between students and teachers need to be restored,” he said.


Meanwhile, school probers are using social media as tools to nab perpetrators.


“Evidence from cellphones, which have become hand-held computers capable of accessing sites, such as Kik, iMessage, Twitter, Facebook, Snapchat, Instagram and WhatsApp, as well as e-mails, text messages, and photos, play an important role in investigating inappropriate relationships” — especially when students refuse to cooperate, SCI told The Post.


“Parents and guardians should monitor their children’s cellphone usage and, at a minimum, question, if not report, any suspicious activity.”


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