We leverage a nationally-representative and previously unpublished dataset on the learning outcomes of 101,084 public-school students in grades 4, 6, and 8 across 18 Indian states and one union territory to diagnose their mathematics skills. Importantly, these data allow us to diagnose their achievement not only in commonly assessed skills (number sense and arithmetic) but also on less frequently assessed skills (geometry, fractions and decimals, measurement). We use a novel psychometric approach to estimate the share of students who can meet fourth-grade standards. We find that the mathematics skills of Indian children may be even lower than previously documented. These children also make less progress than believed. We also document how gender gaps in these skills emerge between grades 4 and 6 and persist in grade 8. Our results indicate that the learning crisis in India may go further than previously diagnosed.