It was good until it wasn't - Janitor Sizer School Employee Review

I worked for a year and a half with no complaints, no compliments, essentially no word from my boss on if I was doing well or not for a year and a half. My boss never communicated in a meaningful way. Then in the last few months of my employment there were many complaints from my boss. I stepped up my work but the complaints continued, even when given a reasonable explanation for what he complained about, it didn't matter. Then I made the mistake of complaining to my bosses boss that he had some problem with me and I wanted to know why. I did not receive a reason and was was fired instead. I'm not the only one who's been fired for raising a complaint to management. They just don't care and don't want to hear it.