The number of hours in a school year varies because each state sets its requirements by law. There is no nationally mandated number of annual instructional hours in the United States.
Some states set a minimum number of instructional days without a set guideline for hours per year. According to the Pew Research Center, the average number of instructional hours in U.S. schools is 943 for first graders, 1,016 for seventh graders and 1,025 for 11th graders. Most other countries have the number of instructional hours per school year mandated by their national governments, but in the United States, education is the provision of the individual states.