Peggy,
There have been lessons that I have found frustrating, but I agree, none that I thought were unsuccessful. When there are more than one adult in the classroom, making sure there is only one voice at a time is very hard for the other adults to understand and follow, this is something I’m working on myself and with my teaching assistants. I also make sure the K in my lesson is clear, as a lot of times the reason of my frustration in the lesson is because there are too many K’s.
Dana