Most fourth graders are around 9 years old. Most children start kindergarten at age 5 and progress through one grade each year. Variances in state age requirements and birthdates may impact the age of children in fourth grade.
The majority of U.S. states have a kindergarten entrance age - the child must be 5 years old before a certain date to enter school in a particular year. In the majority of states the cut-off is in September. Vermont's cut-off is as early as January and Michigan's is as late as November. Each state also has a compulsory age by which children must be in school. These compulsory ages vary state to state, from 5 up to 8 years old. All of these factors affect the age of children in each grade, as does students who are held back or skipped ahead of the grade they should be in.