The Membrane in a cell lets good things into the cell and takes bad things out. In a school the doors do the same, they open and let good things in and let bad things go out.
A Vacuole in a cell is like a storage place, like were yo keep things. A Vacuole in a school is the supply closet because it stores all of the supplies the school needs.
Mitochondria in a cell provides the cell energy. In a school the Membrane would be the teachers that work, because without the teachers, the school would be a failure.
Ribosomes in a school would be the lunch room because in a cell the Ribosomes in a cell provide protein, and a lunch room provides food and protein for the kids.
Chromosomes in a cell carry all of the genes for the cell and that would be the students for the school, because without the kids the teachers would not be able to teach.