Working in private schools?

Dispatch companies that hire English teachers (I guess ALTs) to private junior high and senior high schools have started taking an interest in me. The pay looks pretty good, but what about the working conditions such as conduct and dress code? How big is the margin of error? Is a teacher likely to get fired for nonsensical reasons such as yawning in class, or eating a different lunch from everyone else? I have heard some good stories about private schools, and I have heard some bad stories. What's the real story? What are your stories?

I'm just a parent of a private senior high student, but I've never heard of teachers getting fired just because (s)he yawned in class or ate a different lunch. Dress code, I notice all male teachers wearing suits at all times, unless (s)he is helping a sport activity. In fact, I find the ALT's clothing very original with different ties or great color coordination. Makes the students look forward to class. That's my story from Yokohama.