broken subway

[Cortana]

I am teaching my in real life students in a lab class when the equipment breaks. I get frazzled and run around trying to fix things. Then I remember to hand out quizzes, I don't have enough, and when I return with extra the class has left. In their place is students from my next class I still need more quizzes. I am distracted again, and when I look up again all of the students have boarded a subway train. I see some in the nearest car, I go on for a moment to get them to come back to class. They get off with me. I then realize the train doesn't move, so I get back on to look for my students. I end up at the end of the train, which is a car that has been split in half opening into a cavern of broken roads and concrete. People come and drop off poisonous things there, like batteries and used oil. There are people living in the cavern that try to dispose of everything properly. I am trying to help clean up the toxic junk when I get distracted by a friend appearing, and wonder out of the cavern with him, back to my office at school.