In this review of The New Teacher Project’s (TNTP) “fact sheet” on value-added (VA) analysis, Di Carlo argues that while VA models are sophisticated and have a lot of potential, we have no idea how they are best used or whether they will work. It is likely, he says, that poor models implemented in the wrong way would “penalize” critically large numbers of teachers for reasons beyond their control, as well as generate estimates that are too unstable to be useful for any purpose, even low-stakes decisions. Given that TNTP is actively involved in redesigning teacher quality policies in dozens of states and large districts, Di Carlo is disturbed that they don’t seem to know the difference between real risks and “myths.”