Jan worked really hard with her seventh graders. She was lucky. They were a bright, motivated group and their test scores went through the roof. Her TDR was extremely high. Her principal was very pleased.
Because Jan did such a great job with these kids, the Principal had her follow them to the eighth grade where their success continued. These kids hit the ceiling in seventh grade so there was no room for improvement on their eight grade scores and Jan's TDR gave her a zero.
Jan wasn't concerned. She had already been accepted at a very prestigious college and was going to pursue a PHD. Her principal told her that was a wise decision. The a TDR of zero there was no way he could grant her the tenure she deserved.