Well, I have to say that I'd like to be able to enjoy the option of dodging those goofy public appearance events. I wouldn't sweat it if I were you about not being asked to attend those things. Where I'm working now, they force us to attend those 'special events' on Saturdays after we'd been teaching several classes that day.
Koreans are what they are and it's a sad fact that they often discriminate against those who aren't white, but they are not alone with doing this in the region. Frankly, there's nothing you or anyone else can do about it. It's a situation which may change over time, or more likely not change at all.

What you want to do is try you best to complete the contract to avoid anyone at your current school badmouthing you online, or worse, blacklisting you in a regional work immigration office. Even if they don't go down the road of trying to blacklist you, a record of an uncompleted work visa will be registered under your name at the immi office, making it more difficult for you to obtain a better job in the future. Common ESL Korean employers (both private and public) can freely access this data as I've been asked about an uncompleted work visa which I had in the distant past numerous times. BTW, what's the name of the specific public school you are having a bad experience with?