Third graders attending public schools in the U.S. are generally eight years old. However, some third graders turn nine years old during the school year.
The Kindergarten entrance cut-off age in the U.S. varies from one state to another. In most states, a child must be at least five years old before starting school. Therefore, children are typically at least eight years old by the time they enter third grade. There are a few exceptions to this generalization. If a child skips a grade, he might be younger than eight. Additionally, if the child is held back, he might be nine or ten in the third grade. Homeschooled children are not required to follow the same educational timeline as children attending public school.