Confidence votes 2.0K. Children begin elementary school at age 5 when they enter kindergarten. Most elementary schools go up to 5th grade, and most kids are 11 by the time they finish that grade. But some elementary schools go all the way up to 6th grade so there are kids up to age 12. Then there are even a few elementary schools that only go up to 4th grade so the oldest kids are only 10.