I'm reviewing just this volume.
As a general impression, I'm surprised by how quickly the situation has worsened to critical levels. You could have expected this degree of mayhem and implosion of the local population near the ending of the second act, but not by the third volume of eleven. The author doesn't give his characters a break.
By the end of the previous volume (or the beginning of this one, I can't be sure about anything anymore), our kids, led by the protagonist (who is clear-headed and strong-minded beyond his years), have found buried shallowly in the sand near the school's entrance the missing plaque with the school's name, along with, most importantly, a memorial to the more than 860 children and teachers who perished. The plaque has crumbled after a long, long time under the sun. Turns out the school was teletransported to the distant future. Curiously this improves the kids' mood: their parents haven't been killed by whatever nuclear disaster turned everything into a sandy wasteland; instead they just died due to the passage of so many years that their bones probably disintegrated. This means that their parents are still alive, in the past. Which is true of everyone who ever existed.
In any case, the remaining adult teachers, once they learn that nobody is going to save them, lose their shit. One of them, the most intelligent seeming, slices his own throat in front of his horrified colleagues. Our protagonist's homeroom teacher, who had seemed decent enough (for a schoolteacher), begs for someone to restrain him before he does something horrible. They refuse to do so, and instead they attempt to drag him somewhere to calm him. He proceeds to strangle an old colleague of his (probably the headmaster). After that, the headroom teacher murders offscreen every single other teacher. By the early beginning of the third volume, the only adults that remain alive are this sudden mass murderer and the former guy in charge of the food (who had been restrained by a group of determined kids and locked into some convenient cell-like space).
The murderous teacher gathers the kids to tell them the news, though keeping to himself that he was responsible for his colleagues' demise, and convinces them to work together to survive this impossible situation. He enlists the willing protagonist and a bunch of his friends to drive one of the teachers' cars as far enough as they can, in order to figure out if there's anything out there beyond sand. Far from the school, after they get out of the car and wander for a bit, the kids discover that one of them, the last in line, almost died after someone wrapped a piece of plastic around his head. He warns the other kids about the murderous teacher, but it's too late. The guy, after he fails to kill the kids by hand, gets on his car and attempts to run them over. He kills a couple of them Carmageddon style. Our protagonist was lagging behind, as he was helping a random blonde girl with a limp. They attempt to escape through some caves, only to discover that they were the half-buried remains of the top suites of a still standing hotel. The teacher catches up to them, knocks the blonde out and then starts strangling the protagonist.
The narrative cuts to the distant past to follow the protagonist's mother. The morning when her son disappeared they had argued heavily, and she had told him to never come back home if he so wished. Now his son has disappeared and she blames herself for it: if she had never said something so awful to her dear son, the school wouldn't have exploded. She realistically suffers a psychotic break in which she hears her son calling for help. Because this is a fictional story, turns out her motherly powers allow her to track down her son's cries for help up to the suite of the still standing hotel. She freaks out the couple that had rented the room, as she believes they had kidnapped her son and were about to kill him. She realizes that something more otherwordly is going on, but in any case they throw her out of the hotel. She decides to don a costume, rent that now empty room and hide the protagonist's (who is, let's recall, a child) favorite hunting knife. She wraps it in plastic so it won't decay (how do you know he was transported to the future?), she opens a hole in the wall and hides the knife there. I'm surprisingly fine with the protagonist's mother being able to bridge spacetime with her motherly powers.
Back in the story's present, the protagonist, close to death, grasps the knife her mother left him, and plunges it into the teacher's neck. The guy falls forward into empty space, though we didn't see him die. A proper punishment for his choice of profession.
Our protagonist and his blonde pal come back to the school only to discover that the surviving children, now deprived of adult guidance and faced with the prospect of dying of thirst or starvation in the middle of a desert, have proceeded to the next logical step: they crucify one of the children, light a fire under his feet and intend to stab him with spears so his blood, on contact with the flames, will bring forth the rain. The protagonist has had enough of this shit, in general. He goes back to his classroom, where his classmates are complaining about lacking water and food. The protagonist suddenly remembers that the school has a pool, a fact about their surroundings that every other one of the hundreds of children managed to forget. After realizing they have a supply of water for the time being, the kids remember that they have pockets in their clothes and that they used to stuff them with food. They gather everything they can find. Now they will be able to drink stale, chlorinated water and trash food for a few days. I think that the protagonist uses this fact to convince the suddenly formed cult of murderous kids to knock it off. Maybe he convinced them in some other way, I can't remember. In any case, he gathers all the students his age in the gymnasium and he gives them a surprisingly adult speech about how the real adults couldn't handle having been transported to the future, because the adults' minds have solidified into logic and reason, but kids can adapt to any situation, and that's how they will survive, or something. He convinces them to act as father and mother figures to the children from the lower grades. The main female classmate proclaims that she's eager to be a mother.
Shortly after, one of the kids the murderous teacher had ran over had staggered his way back to the school just to give the protagonist an alien-ish leaf and then die. Starving as he was, they find out that he had stuffed his mouth full of sand. Apparently when one is close to starving to death, sand looks appetizing. Meanwhile, one of the dumber kids had been given the task to feed their adult prisoner (the food delivery guy who had attempted to wasteland warlord his way out of this situation). The guy convinces this dumb kid to give him some wire, and he picks the lock of whatever cell-like space he was in. He pushes the plate of food against the kid's face and then kicks him to the ground. As the protagonist was about to share the discovery of the leaf with the other children, the adult, armed with a knife, comes out and proclaims that as the only adult, he will act with the kids however he damn pleases. Learning about the leaf, somehow they convince the extremely hostile adult to walk together in the direction the kid who starved had come from. Along the way they realize that the adult doesn't know that they've been transported to the future, and predictably, being told so only causes him to kick and beat the defenseless children. Suddenly they stumble upon an alien-looking "forest", something of an oasis. Turns out enough time has passed for horrible monsters to evolve (or the author cared very little about making this realistic), and they end up being pursued by a terrifying, enormous centipede-like thing. The bad guy knocks one of the kids to use as bait, and then they attempt to escape. Some of the shittier kids betray others. Even the adult gets molested by the creature.
The narrative leaves those people behind to follow the kid who had betrayed others to survive. As he arrives at the school, the female classmate who couldn't wait to be a mother can't believe the protagonist is dead. With the de facto leader gone, some others step forward to fill the void of power. Turns out the school had a girl gang, and its leader, a nasty, older looking girl, establishes her dominance by clawing a male kid's face and then stripping down and allowing one of her henchgirls to crush another kid's nuts. As the new leader of this doomed population, the girl proclaims that she'll execute whoever had stolen food and left a shoe behind. One of the children runs away, and they pursue him. Turns out the protagonist and most of the others, including the adult, had managed to survive the encounter with the monster, and had staggered their way back to the school. The gang of girls clash with the protagonist. The delivery man can't adult anymore; the encounter with such a horrifying creature, combined with discovering that he had been transported to the future, had literally turned his mind back into a toddler's. In any case, the volume ends with a memorable focus on the kids from the lower classes, who, having fallen into psychotic depression themselves, have gathered on the roof of a nearby building to yell, cry and proclaim that they'll fly back to their parents. One of the children states that he'll turn into a bird, and jumps off. The panels follow him falling down with a determined look on his face, only to splash against the concrete. His classmates, up on the roof, look up to the sky, tears in their eyes, and proclaim that they can see his fallen classmate as he flies towards freedom.
What an entertaining series. It keeps hitting you with charmingly crazy shit and what passes for deadpan humor (which probably wasn't intended), such as the reactions of the protagonist to watching other children spearing a crucified child, or his female classmate eagerly offering herself as a mother, or the limping girl's introduction full of unasked exposition about herself travelling alone towards whatever is left of her hometown (only to be told by the protagonist that she's walking in the wrong direction), to the deranged adult delivery man claiming that children are like beasts and he can do whatever he wants with them (to the bafflement of the all too conscious children), along with many other little moments that unfortunately I can't recall, and that had me giggling to myself on the train to work. This one is a deserved classic.