Pity my DD's supply teacher today. Arrived late for the maths lesson. Class already bouncing off the walls. Rushes in carrying bag, books, large full coffee cup, etc. Puts down bag, turns around... trips over bag ... coffee cup goes flying ... all across the blue carpet.
Then she swore.
Shortly after that the teacher from next door came in to find out what was going on!
I am supply at the moment. Being late for class is not always avoidable; you may have only just been given your assignment for the period. Hot drink outside the staffroom, very avoidable and downright dangerous.