The constructs that currently animate today's dispositions movement are grit and growth mindset. However, the evidence for the reliability and instructional uses of such noncognitive factors in K-12 schools--and of the surveys and tools that attempt to measure them--is thin. After a look at the "logic of assessment" with its focus on cognition, observation, and interpretation, the author concludes that the noncognitive data and metrics used by reformers to support decisions to group schools by levels of grit or place students in particular interventions to improve mindset must be validated with common sense and a body of technical evidence.