Very good start. The graphics are pretty good and the engine seems to run fine. I had no glitches or freezes. Enjoyed it. The concept is good.
I wasn't too sure about the Suspicion and Mood bars. I assume they relate to how the students see you, and they probably have something to do with how successful the teaching is. Explain it a little better in-game?
A few ideas:
More items to buy in the stores. I owned everything like half-way through the game, and after that money was useless. Maybe some Advanced Teaching books to rises stats further. Or add some food and drink at a restaurant that you can use to raise your energy level a little bit without sleeping. Granted, it would only be enough to do one or two more things. Maybe you can only buy food once or twice a day, to be sure that the player doesn't forget to sleep. Also, it would be cool if you added items that the player had to buy or risk losing the game, such as food and groceries.
Add a teacher's lounge to the school. There we could chat with other teachers in the school, get advice, and go on dates or other outings. Dates would use energy and have other benefits, but the player would have to choose whether or not it was worth wasting teaching time, as teaching is the main object of the game.
Have a few cases where we go back to the apartment and meet people before we can sleep. Maybe the landlord arrives every 15 days and asks for rent, or friends drop by and ask you to go out, which would result in getting energy from sleeping. This is similar to what I said above: if money was necessary to complete the game (don't get kicked out of your apartment, buy groceries or starve), this would make it even tougher to balance working hard and goofing off.
The grading curve should probably be a bit steeper. My students were acing all their classes even before I got to 50 in each category, but I ended the game having about 170 in every skill. You might want to raise the benchmarks.
Possibilities are without limit.