During a test, teachers work to maintain a safe, cheating-free environment for the students so they can focus on the test alone. At the same time, teachers are planning innovative new methods to teach students on the next topic. Maybe, teachers are studying the test itself, to be better prepared to answer questions about it from students once the students get the test back. Time and time again, AATB (through my inferences about her,) has given tests that strengthen the mind by making students consider whole new possibilities, often making the students have diverse philosophical experiences.
Such is the test day for the teacher.
Or, they are listening to music loudly, like my elite AP World History teacher, who coined the phrase, "Test day...is the best day."
