Sum Ting Wong? A New York teacher who investigators say had sex with a student was able to exploit loopholes and delays in the disciplinary system to land a teaching job in New Jersey, The Post has learned. Jinwoo Seong, 36, repeatedly grabbed a male student’s crotch, exposed himself, had the youth stroke him and engaged in oral sex while a special-education math teacher at Martin Van Buren HS in Queens, according to an explosive eight-page report by special schools investigator Richard Condon. The student cried throughout an interview with investigators. Seong also touched a girl’s breast and crotch over her clothes, slapped other boys’ butts, hurled obscene comments and made “gay jokes,” the probe found. One girl told investigators that Seong asked her to measure a classmate’s penis during an after-school tutoring session. Another boy claimed Seong kicked him in the testicles when he cursed the teacher. But Seong, who was fired, managed to get a new job in Jersey simply by not revealing his troubled past. The case shows how a teacher accused of shocking misconduct can slip through bureaucratic cracks and back into the classroom. Condon’s nine-month investigation ended last Sept. 28 with a letter to Chancellor Carmen Fariña, saying Seong “has no place in New York City schools.” But Seong, who was assigned to a “rubber room” pending the probe, remained on the city payroll until the Department of Education terminated him on Nov. 30. The untenured Seong denied the charges but was not entitled to an administrative trial. Seong used his time in the rubber room to scramble for new employment. In October, New Jersey granted his application to recognize his New York certifications to teach special-ed and math in grades 7 to 12. Seong then found an opening at Don Bosco Technical Academy, a public middle school in Paterson, NJ, telling officials he wanted to “relocate.” As soon as his NYC firing was official, he accepted the $62,000-a-year position. He started on Dec. 7.