We found a major bug! We just fixed it.
In the previous update, we introduced a new rule in which children that are missing subjects in their schedule once classes start cost -$100 at the end of the day. (Translated: you get penalized if you don't have enough teachers at the start of classes.)
HOWEVER, there was a bug that applied this penalty after firing teachers at the end of the day. This has been corrected. You will never be penalized for firing teachers so that you do not have to pay them.
There's a few other bugs, which can be found in CHANGELOG.txt