Whose exams are harder in high school, the USA or the UK? 

It's difficult to make a direct comparison between the difficulty of high school exams in the USA and the UK, as the education systems and curricula in the two countries are quite different. However, both countries have rigorous academic standards and challenging exams. 

In the US, high school students typically take a range of standardised tests, including the SAT or ACT college entrance exams, Advanced Placement (AP) exams, and state-level assessments such as the Smarter Balanced Assessment. These exams cover a variety of subjects and are designed to measure students' proficiency in key areas such as math, science, English language arts, and social studies.

In the UK, high school students typically take a series of exams known as the General Certificate of Secondary Education (GCSEs), which cover a range of subjects including math, English language and literature, science, and social studies. After completing their GCSEs, students may choose to continue their studies and take additional exams such as A-levels or vocational qualifications.

Overall, both the US and UK education systems place a strong emphasis on academic rigor and challenging exams. However, the specific content and format of these exams may vary, making it difficult to determine which country's exams are "harder" overall. Ultimately, the difficulty of high school exams will depend on the individual student's strengths, weaknesses, and academic goals.