Subbed for high school math. I had three blocks of Algebra 1 and one block of study hall.
The plus side is that I relearned the difference between the substitution and elimination methods of solving a system of equations. I think it is fitting that I like the substitution method better.
The down side is that my notes for study hall said, "They should be working on homework or reading a book - they should be silent the entire hour." Guess how many students actually walked in with anything in their hands. .