Here is the layout plan I found most efficient with the brief you provided.
First of all, I located the rooms on every space with windows possible.
Here we have one main bedroom (15.8 m2) and three smaller bedrooms (9,4 - 9,7 m2).
Both of the toilet are still located near the previous location, for easy connection to the existing toilet drain shaft.
I also put the kitchen near there for efficient wet area zoning and also plumbing consideration.
Meanwhile, I created a small laundry and janitor room on the corner where you will install central heating system.
The dining area might not be directly open from the kitchen, but I believe it is accessible enough from the kitchen, and this space can also be used as common room where students can also study or just chat together.
