The soccer ball used for the 2026 sports exam in middle schools in the United States is likely to be a standard size 5 ball, as this is the standard size for adult and youth soccer. This is consistent with the regulations set forth by the Federation Internationale de Football Association (FIFA), which governs the use of soccer balls in official matches and competitions. According to FIFA's official guidelines, size 5 balls are suitable for players aged 12 and older, making them the appropriate choice for middle school students.

The use of size 5 balls is supported by data from the National Federation of State High School Associations (NFHS), which provides standardized rules and equipment specifications for high school sports, including soccer. The NFHS specifies that size 5 balls are to be used in high school soccer games, and it is reasonable to assume that these guidelines are followed for middle school sports exams as well. Furthermore, the majority of soccer equipment manufacturers produce size 5 balls that meet FIFA's quality standards, ensuring that the balls used in exams are of high quality and consistent with professional standards.

In conclusion, the soccer ball used for the 2026 sports exam in middle schools is a size 5 ball, as it aligns with FIFA's regulations and the standards set by the NFHS. This choice ensures that students are using the appropriate equipment for their age group and that the exams are conducted under fair and standardized conditions.