You’re reading Back of the Envelope, an experiment that aims to bring shorter, quicker content to FiveThirtyEight.A new study shows that first-grade teachers consistently rate girls’ math ability below boys’ — even when they have the same achievement level and learning style. The study out today in the journal AERA Open from researchers at New York University and the University of Illinois at Urbana-Champaign seems to represent a setback for gender equity in math.