Did you know that you can use your students to gauge the phase of the moon? It's true. You see, inevitably, students act up on days with a full moon. Sure enough, today my students were a bit squirrelly. It's not that they're bad. No, they're just excited.
Did you know that the same thing happens with a barometric pressure change? Yep. If there's a massive weather system going through, you'll know because of your kids.
Did you know that weather changes also do it? The first warm day of the year can be awful!
All of this is to say that students are humans. They change day to day. Some days are worse than others. You can't expect each class to behave the same way every single day. See, we make these excuses for why students act up. The reality is that students change and sometimes even have a bad day which spreads to the rest of the class. Keeping this in mind can help you keep your cool and adjust your lesson plans on those crazy days.
And remember, don't hold it against your kids when they're a bit off one day. After all, they don't hold your bad days against you.