In the United States, education is primarily the responsibility of the state and local communities. As school districts arrange their calendars and outline their curriculums, it’s important to take into account what is an appropriate number of hours spent in school. One way of categorizing that time is by hours per grade level. As we can see in this graph from the team at Playground Equipment, a portion of states have kindergarten programs with almost half the required hours of schooling as their grades 9-12 counterparts. One could infer that maybe younger students whose brains are still developing gross motor skills and processes don’t need as much time in a formal school setting. It’s commonly noted that the attention span of adolescents is the shortest in the younger years, which is why you’ll see many states offer a half day kindergarten program. On the other hand, other states such as Texas, Rhode Island, Oklahoma, & Alabama require all students to attend the same number of hours of school per year, regardless of grade level. It could be argued that the more time spent in a controlled learning environment the sooner a child will retain that knowledge. Nonetheless, setting educational hour minimums is a common practice among states, and will be done in the way that best suits the needs of the people living there.