Wiktionary
redshirting
vb. (present participle of redshirt English)
Wikipedia
Redshirting (academic)
Redshirting is the practice of postponing entrance into kindergarten of age-eligible children in order to allow extra time for socioemotional, intellectual, or physical growth. This occurs most frequently where children's birthdays are so close to the cut-off dates that they are very likely to be among the youngest in their kindergarten class.