We provide causal estimates of the effects of delayed kindergarten entry on achievement outcomes by exploiting a policy change in the birthdate enrollment cutoff in North Carolina that forced children born in a six-week window to redshirt. Using multiple peer group comparisons, we identify impacts on achievement and gifted or disability identifications in third through fifth grades. Delayed entry provides small benefits to students' math and reading achievement, and reduced identification of a disability; these impacts operate through cohort position and age advantages, and not from hold-out year experiences. Redshirting differentially benefitted low-income students, but further disadvantaged non-white students. [This research depends, in part, on data infrastructure partially funded by the North Carolina Department of Public Instruction and the North Carolina General Administration.]