Now, I have noticed that there is another way of getting out of the boss fight of the school other than the portal: The Door. We first see The Door. show up at the start of the game with Ms. Slithers warning us against it. Ms. Slithers doesn't lie (juice isn't stupid) and cares for the player (monitors juice kid at playtime for safety). The Door. doesn't seem to be bad for us though. 

     I, in hope, suggest a continuation of The Door. after the Ms. Slither boss fight (with her tough loving aura being gone). The point of no return would be when the player gives their hard earned juice to The Door. The playground darkens, the music muffles, the juice portal disappears, the ability to fly vanishes (jump is still there), and the player/juice kid gets greeted by a hallway behind the previous The Door.

The hallway is long and tall, with plywood walls and swirling red carpet originating from another The Door. from the end of the hall.

    The player going near the new The Door. gets told to look at it directly to talk to it, learning The Door. wants more than simple raw juice. It wants concentrate. Give other monsters your juice and they, after death, give the player concentrate. (item or a value)

    Turning back, the player is no longer looking at the school but a hazy unending room with plywood jutting out of the carpets and the tooth ceiling Idk, The Door. has teeth. having random teeth poking out from it. The swirling red carpet doesn't distract from the slow moving enemies. The player/juice kid would then have the ability to give juice to the monsters by holding space (a single press would be a jump). The more juice, the more concentrate and harder the monsters will become. 

    When juice kid finally gets enough concentrate, a new song will fill the air. It would be The Door. singing so you can find your way back. The player would then be able to escape, with The Door. singing a portal in front of it. Ingot then remarks that you look like Ms. Slithers gave you a wallop, and "borrows" your left over concentrate.

• A different way in starting this could be sleeping at the desk first, and then going to The Door. in the dream realm (with floaty gravity to help with jumps)
•  The teeth ceiling is pretty dumb, ceilings are hard.
•  The suggested new mechanic is secondary to getting a cool, new, non-euclidean room. 
• With no flying suggested, it could be a Supa Hard [TM] boss refight dream arena if totally new realm ain't doing it for ya. 
• I have a "tongue bug" monster idea, though custom monsters would probably be too jarring with the new mechanic After enough concentrate is collected
• The Door. has great lore potential

Thank you for reading, and I hope that you agree that something akin to this would be cool in the game