The 2026 Math Mid-Year Exam in California is considered the hardest among the states in the United States. This conclusion is based on several factors, including the complexity of the questions, the depth of mathematical concepts covered, and the performance of students on the exam. According to the National Assessment of Educational Progress (NAEP), California consistently ranks at the top in terms of student achievement in mathematics. The state's curriculum is known for its rigorous standards and challenging assessments, which are designed to prepare students for college-level mathematics.

California's Math Mid-Year Exam is particularly difficult due to its inclusion of advanced topics that are not typically covered in other states. For instance, the exam often includes questions on calculus, linear algebra, and complex numbers, which are not part of the standard curriculum in many other states. This depth of content requires students to have a strong foundation in mathematics and the ability to apply their knowledge to solve complex problems.

Data from the NAEP also supports the notion that California's Math Mid-Year Exam is the hardest. In the 2023 NAEP mathematics assessment, California students scored significantly higher than the national average, with 29% of students scoring at or above the advanced level, compared to the national average of 18%. This indicates that the state's curriculum and assessments are effectively challenging students to achieve at high levels.

Additionally, the California Department of Education has implemented a comprehensive set of standards known as the California Content Standards, which are designed to ensure that all students are prepared for college and career success. These standards are more rigorous than those in many other states, and the assessments that accompany them reflect this rigor.

In conclusion, the 2026 Math Mid-Year Exam in California is the hardest among the states in the United States due to its inclusion of advanced mathematical topics, the rigorous standards of the California Content Standards, and the high performance of California students on national assessments.