Hi! I'm very new at this, so feel free to completely ignore this, but my opinion as more of an artist is that its very unbalanced. what should often be the center of gravity (the doorway) is far away from the busiest part of the scene (the lunch counter.) it's really good that you gave the room shape, as boring, square rooms rarely look great, but you just need to balance it so that it looks more like a big open space, and less like the state of New York.
It also feels very small and cramped in places, especially near walls and furniture, and the tables look like they only seat 40 people max, which didnt seem big enough for a typical school. It's also quite overdecorated, which adds to it feeling cramped. you could just tone down the wall tiles and space thing out a bit more. Adding doors and windows also help make the room feel a bit more open, and like the lunchman isnt trapped there. Having a mirror in a cafeteria just felt kinda weird, so I just made it a shelf or smtg.
These are just suggestions again, but I made a couple of VERY SLOPPY edits in paint just to illustrate what I'm getting at. It's quite similar to the original, just following my own suggestions to balance it out.

and the second is a larger version, because I felt it was still too small and narrow.

I hope this doesn't come off as rude or anything! feel free to correct me on anything.