Welcome back, class. I know the first day of school after break is sorta useless, and I know it's hard to remember things we talked about two weeks ago, so...
...so you just lost a day of teaching.
Look, it's not like I'm blind or stupid. I notice the days that are more difficult to maintain student focus. Typical culprits include days immediately before or after a scheduled vacation or a major non-academic event like the state championship football game or the prom. I know my seniors will engage far better in the fall than the spring, while freshmen are the opposite.
Fact is, these difficult days are still school days. I've still got a job to do; the AP exam or the class final doesn't get pushed back because of last night's Duke vs. North Carolina game. These days will never be as effective as an ideal day.
But that doesn't mean simply punt on them. Have a plan. Do something as active and engaging as you can manage. These aren't the days for long discussion or lecture sessions, not for testing, not for difficult creative lab work. These are good days, however, for straightforward, active lab work. For one of those The Physics Classroom interactives. For starting a new topic with an eye-catching demo showing a discrepant event.
No matter what your plan, though, your demeanor is the most critical component to the quality of your class on a difficult school day.
Why do students consider that, for example, they shouldn't have to think too hard in class the day after the Super Bowl? Because all the adults around them say so. (Not, in the vast majority of cases, because the students were out drinking and climbing greased lampposts until 5:00 am the night before. Philadelphia-area schools possibly excepted.)
If you start class with a pre-made excuse to not pay attention, well, why are you surprised or disappointed when the students don't pay attention?
Keep calm and carry on. "Did you see that game last night, Mr. Lipshutz?!?" "Yes, it was fantastic! I'd love to talk through the Eagles' gutsy playcalling at the lunch tables - amazing. For now, though, here's our three minute bell quiz which will remind us of last week's topics... you may begin."