I hate to say it, but I can sort of imagine Natasha Vaynblat, when she was Ms. Vaynblat, coming off at first as the teacher who could be walked all over. She’s nice, cute, and says things like “oh my gosh” with complete sincerity, but her unassuming nature belies her comic demeanor. During her four years as a teacher (she left the job in 2013, for comedy), Natasha loved to prank her students. In “United Federation of Teachers,” her first one-woman show at UCB Chelsea, the audience gets to see both her victories over troublemakers and her hilarious miscalculations, all of which remind me of the myriad reasons why I’ll never willingly put myself in charge of children. B+B spoke with her over the phone about her experiences and her new show.