Billy Porter’s version of high school life makes the fashion-forward kids in “Clueless” look like the orphans in “Annie.” The Tony and Emmy winning “Pose” star’s students in “Anything’s Possible” are dressed to impress, sporting fabulous wardrobes that are more Broadway than biology class, even if the senior class looks old enough to be the teaching staff. That’s the case with Kelsa (26-year-old Eva Reign), who is officially the least convincing high schooler since Ben Platt strolled through his cafeteria in “Dear Evan Hansen.” But if Porter’s surface details are off, “Anything’s Possible” get…