I HATE subbing on my prep hour. I know it is the 'right' thing to do, take one for the team, blah, blah, blah...
#1 I have things I NEED to do, things I want to do, and sometimes, just time to decompress from having kids all day. I NEED that hour to maintain my sanity.
#2 Lesson plans vary from good, structured and 'keep 'em busy' to non-existent.
#3 I don't always know the content and don't have time to figure it out as students are asking questions.
#4 and probably the biggest.... different teachers/different classrooms/different expectations for behaviors. While I do not believe classrooms need to be quiet for learning to occur, I do believe there needs to be some level of peace and structure. Some classrooms run quite differently from my expectations. Trying to have students conform to MY own structure for a one hour period, is often impossible, especially on a Friday afternoon.
So here I sit.... yes, subbing on my prep, wishing I'd just said NO!