Jessie's ma sends Jessie out into the world in her stead. This might seem cruel considering she could have gone herself as an educated adult who knew it wasn't 1840, but after multiple pregnancies just couldn't fit into her old clothes anymore. But she kept them—and was smart enough to hide access to the "future" from not only the cameras, but from her own husband who was too deep in the Masquerade. She never trusted they were safe in the village and so made sure there was some form of access outside of their town.
Jessie's mom puts her in clothes from the 1980s, hoping they're still in fashion—jeans and a T-shirt. However, the jeans have flared legs and are bell bottoms. The '90s actually had multiple fashions that were a look back to The '70s. Jessie just appeared to be in retro fashions of the time that many teens were wearing.
Jessie's mother had to send one of her children out into the real world without any guidance other than what she knew from before. What if the henchmen had successfully hurt her, or Jessie had been sicker than she realized and died? Jessie would have never came home, and multiple children would have died of a curable disease—all so the Mad Scientists could keep trying to make humanity "stronger" by exposing them to curable diseases. As it was, two children did die. Furthermore, how many more diseases would the scientists have tried to expose the village to if they hadn't been caught?
As it was, the village was isolated for almost two decades. How many women might have died in childbirth to preserve the "authenticity" of the village if things had continued on? Did any at all?
Jessie's father is so deep into the Masquerade after being beaten for Jessie coming across the cameras that he had to go to a therapist before he was allowed to reunite with his kids, and all the children were taken from their parents and arrested for their part in keeping the truth about Clifton a secret. The schoolteacher Mr. Steward even threatened to shoot the children, including his own son, rather than let the police take them from Clifton. How many parents—one or both—were so deep in denial or so tied to the Masquerade they didn't get custody of their kids back? How many might have harmed their kids for integrating into the modern world if they did?
Jessie's Pa was beaten up severely when Jessie, as a curious child, came across one of the cameras that broadcast their village to the outside world. She was told he'd been kicked by a horse. Because of this, he ends up so deep in the Masquerade that he Cannot Tell Fiction from Reality. It's likely other parents have been punished this way to the point they had mental breaks, and some children's parents may have just died in "accidents" if the men in charge wanted to ensure their silence. Frank Lyle was willing to kill Jessie, a child, so he likely wasn't above killing adults.
There's a whole lot of children (and young adults, who may have been brought there when they were too young to have solid memory of the outside world or were brought there before they started school) who have grown up believing that it's only 1840 now and have to suddenly become part of 1996. They—like Jessie—have to learn over 150 years of world and American history. All about World War One, World War Two, Civil Rights—and the Civil War itself. That's a lot of history to catch up on, and many aspects are deeply unpleasant.
Race-related—when Jessie gets to the outside world, she meets Nicole, a black girl, and briefly considers commenting on how surprisingly smart she is and asking her what it's like to be a "Negro." Fortunately, she doesn't get a chance to actually say it—but there's a lot of children who are now part of society who will have a chance to interact with black people and other people of color and are Innocent Bigots—and they might not actually use the word "negro." Furthermore Jessie recalls, upon seeing Nicole among white classmates, that "the abolitionists in Clifton" got their wish with slavery abolished in the "future". Which implies that there's adults who are anti-abolitionists in Clifton—and who most likely taught their children to be pro-enslavement as well.
Frank Lyle—pretending to be Issac Neeley—broke into an apartment that Neeley's phone number had been reassigned to. Bob informs Jessie that the family was fortunately on vacation at the time, so he didn't encounter anyone. What if they hadn't been? He was ready to kill Jessie to keep the secret, after all.
Two children—Abby and Jefferson—still died of diphtheria, despite Jessie's success. Imagine how devastated their parents are, knowing that their children could have been saved, watching them get sicker and sicker until they died—and how regretful they are for not breaking the Masquerade in time. Nothing will bring their children back, even if they sue the scientists for everything they're worth.
