It’s important to be realistic about your strengths and weaknesses and adapt accordingly. An important special case: Grading homework and exams can easily overwhelm the teacher. My brief tenure as a regular, full-time classroom teacher was as a maternity-leave replacement, and by the time I started, I knew I was a slow grader. I had four (count ’em) preps, and getting four lessons ready every day took so much time that I quickly realized that I’d have very little time to grade homework. From the beginning I didn’t try to grade as much homework as the very experienced teacher I was filling in for did. But I couldn’t even do what I thought (and had told my students) I could. It wasn’t until I graded the final exam that I realized how slow I was! I can see several reasons for this: wanting to give students really useful feedback, wanting to grade as consistently as possible, my inexperience, etc. If I teach much more, I’m sure I’ll get more efficient, but not by so much that it won’t always be an issue. But — as Ofer Levy pointed out to me later — the teacher usually has quite a bit of flexibility in how much grading they have students generate. One reason is that there are often ways to substantially reduce the load of grading without harming learning, so the teacher can avoid being a victim of a system they created themselves. Some ways that seem appropriate for teaching math, along with many other subjects: assign group instead of individual work; let students correct each other’s work; go over homework and quizzes in class but don’t collect or grade them. I did some of this, but could have done much more… and if I had, not only would I have been better off, my students would have been too because I would have had more time for their more serious problems.