The second chapter of Little Nightmares 2 focuses on Mono's and Six's journey through a creepy school in the Pale City. In there, you'll find one of the game's antagonists, the teacher. This lady looks like a 1910' teacher, but with a huge head and a long neck, she can stretch and bend, similar to a snake. There are also the students, little bullies made of porcelain that will attack you on sight.
During chapter 2, you'll be able to find two hats for Mono to wear, six glitching remains, and five missable achievements. Moreover, this chapter includes five different puzzles you'll have to solve to keep progressing throughout the area. Here's how to solve them:
TV Puzzle
This puzzle is the first one in the chapter, and you'll have to solve it right after entering Pale City. You'll see a bunch of TVs stacked on the floor. Leave them untouched for now.
Go to the hole on the right, and Six will help you jump through it. In this new area, hop on the hanging hook and swing until you knock over the TV on the left. This will pull you upwards and gain access to the second floor.
Go to the rea on your left, where you'll see many TVs hanging from a rope. Push the one that's behind you, and Six will be catapulted to the floor that's above you. Head back to the area on your right where the two of you will be reunited. Now all is left to do is to run and jump towards her.
Entering The School
You'll enter the school via a rope that's hanging from one of the windows (maybe someone was trying to escape the place?), climb it up, and you'll find yourself in a room with a light switch. While it might sound counterintuitive, interact with the switch to turn the lights off.
You can now see a dim light coming from a painting in the wall to the right, almost as if there was something behind. Now head to the hallway in that area and enter one of the open rooms to find and grab something that you can throw at the painting. Once you do that, the painting will fall down, and you'll be able to crawl through the hole on the wall.
You'll be now in a room with only a chair in the middle. Climb on it and then jump down to reveal a trap door. Jump on it, and Six will follow you until the door opens. After that, just continue the only path that's available until you reach the room with the vent, open it up with Six's help and continue walking. Eventually, you'll reach the school's corridors.
Finding The Elevator Key
After Six gets kidnapped, you'll need to find the elevator key to go and rescue her, but before you can find it, you'll need to navigate the teacher's classroom without her even suspecting that you're there.
Once you reach the classroom, you'll have to move through the place while crouching down and moving quietly. The general idea is to move when the teacher faces the chalkboard and then use the desks as a hideout when she looks at the students.
Move around until you reach the door on the right, go inside the room, and you'll see the key at the top of the small bookshelf. Climb on it, and it will quickly fall down (try not to get crushed by it tho), then hurry up and hide in the box that's in the same room. The teacher heard the noise and will check what it was.
Once she leaves the room, the vent nearby will open up, so now grab the key and exit through the vent. Once again, you have to sneak around, this time to get out of the classroom. Once outside, go to the elevator and use the key.
Chess Puzzle
While exploring the school, you'll eventually find a room with a giant chessboard in the middle; you'll see that the tops of some pieces are missing.
First, head over to the right till you see a painting with a red-eye drawn over it and interact with it to reveal the chess puzzle's solution. It turns out that what you have to do is match the pieces in the board to the pieces' position in the drawing on the wall. You'll need to find the queen, the king, and the rook.
To your right, you'll see the queen, so hop over the table and remove the top piece. The rook will be just outside this room, and the king is on the table on the left of the board. Keep in mind that you'll need to place the top of the rook in the piece that's just in front of that table to use the chess piece to get over the table.
Put the pieces in their correct positions, and a light will turn on, then climb on the table on your right and interact with the lamp. A door will open, and the key you're looking for is inside.
Getting The Bully's Key
Solving this puzzle will give you the key you need to open the music room inside the school. You'll find this puzzle when Mono and Six reach the room that has a piano inside.
First, you'll need to interact with the crank that's behind the piano. As you turn it, the piano will be lifted up in the air. Eventually, the piano will fall down, breaking the floor, now jump on it to make it go down to the floor below.
Now go to the vent in the left wall, Six will help you out so you can reach it. In the other room, a bully is playing with a key; you don't want her to spot you, so better use the piece of wood in that room as cover.
Six will make some noise to distract the girl, use that distraction to grab the pipe that was near the bully, and use it to smack her head. Now grab the key and go to the door on the right, Six will help you open it.