Sometimes you hear an explanation of something that reinforces what you have tacitly been doing.
A teacher has a finite amount of time to invest during the week. They can invest time in any number of activities. These include preparing lessons, correcting work, writing comments on work, professional reading, attending professional learning, counselling students, contacting parents. There is never enough time in a teacher’s day to do all these things. A teacher’s life is a series of time based compromises. What will I invest the next 30 minutes of my time doing? There is always a choice and always more to be done than time available to do it.
Writing comments on student work is a non renewable use of teacher time. It benefits one student probably once. Investing time in preparing lessons on the other hand is a renewable use of teacher time. Whatever you prepare will benefit many students and can be reused in subsequent years.
What will I spend time on now, preparation or correction?
Err on the side of preparation, especially if it is something that can be used many times over.
Preparing great learning activities is even better if your preparation can be used by others