I felt pissed reading this because I know how tedious teaching can be and for 3 months! Woah! That is so mean and manipulative.
I felt the brunt of this for a month's job. Mine played out differently though. If there is a thing that will bite one hard it's owing wages.
The upside to it is all the knowledge and experience gathered that will and I'm sure has made you stand out. So sorry you had to go through that.