The total score of the six subjects in middle school varies depending on the grading system and the specific school. However, a common scenario in the United States is that each subject is typically worth 100 points, resulting in a total of 600 points for all six subjects. This is based on a standard grading scale where each subject is graded on a scale of 0 to 100.

The reason for this structure is rooted in the American education system's emphasis on standardized testing and comprehensive assessments. According to the National Center for Education Statistics (NCES), the average score on the National Assessment of Educational Progress (NAEP) for eighth-grade students in reading and mathematics was around 260 out of 500 in 2020. This indicates that each subject is typically weighted equally in terms of grading and assessment. Additionally, the Common Core State Standards, adopted by most states, outline specific learning goals for each grade level, including middle school, which further contributes to the equal weighting of subjects.

Furthermore, the American education system often emphasizes a well-rounded education, where students are expected to excel in various subjects. This approach is reflected in the grading system, which aims to provide a comprehensive view of a student's academic abilities. For instance, the six subjects commonly included in middle school are English Language Arts, Mathematics, Science, Social Studies, Foreign Language, and Physical Education. Each subject plays a crucial role in preparing students for high school and beyond.

Data from the NCES also reveals that the average student in the United States takes around 6.5 to 7.5 credits per semester in middle school, which typically translates to six subjects. This further supports the notion that each subject is given equal importance in the grading system.

In conclusion, the total score of the six subjects in middle school in the United States is commonly around 600 points, with each subject contributing an equal share to the overall grade. This structure is influenced by the American education system's emphasis on standardized testing, comprehensive assessments, and a well-rounded education.