Are you sure you clarified that it was in fact a break and not the end of the lecture? Maybe they misunderstood

I gotta say as someone who's been through uni, three hours in a lecture theatre is a really hard slog, I'm glad mine were usually 1 hour and only occasionally 2... I'm guessing there wasn't a way to break it up into two shorter lectures due to scheduling. Sucks but I do understand why they bailed out.

I thought the brain could only absorb 2 hours of information before it burns out, and everything after that is basically forgotten. So the last hour of your lecture was pretty much wasted anyway.

If they knew it was a break, give them a quiz about that portion of the lecture they missed.

What kind of a monster lectures for 3 hours?

Consider taking attendance during the second half of the class, with grades penalized if people don't stay. Or, be more interesting so people want to stay.

As a second year engineering student I understand their pain. My engineering economics also had a three hour lecture and the prof would try to finish a bit early instead of a break. Most boring class ever, he knew we wouldn't come back if he let us go.

I've had three hour lectures before. My teachers take attendance at the end of class and missing more than 3 days resulted in being dropped from the class. They signed up for it they need to suck it up cause it's usually about 16 classes for the semester.

Ima select both here. Your fault for lecturing for three hours and giving them a break but their idiots for not coming back.

give a test on the entire lecture. then I'm sure they will regret missing the 2nd half