Mr. E said:
Lynnie, our principal (principals, including assistants) just walk in at any time. You kind of know if it might happen one day because of word of mouth. Many principals try to hit a certain "pod" on a certain day (English pod, math pod, etc.).
My principal walked in on my worst class of the day on the Friday before Spring Break right before a pep rally! It was insane. Those kids were bouncing off the wall (I'm talking about 11th graders here). I continued with the lesson and managed them as best I could. Afterward, I asked her (the principal), "Why now? Today?" She said she had to get her evals into the superintendant for the month, and it just happened that way. She said she took into consideration the day, and the eval was glowing. They're not there to get us in trouble, they're just doing their jobs, too. Still, when they walk in I get all panicky, even when things are going great!