The PISA is a standardized international test administered to 15-year-olds every three years by the OECD. It assesses abilities in reading, math, and science by how effectively they apply knowledge to real-world problems, think critically, and apply creativity. The PISA is widely regarded as a global benchmark for education systems, as it compares how students across different countries think, solve problems, and interpret data.

In The Smartest Kids in the World, the PISA functions as the central metric for evaluating and comparing educational effectiveness across nations. Ripley uses it to identify high-performing countries like Finland, South Korea, and Poland and also to raise deeper questions about What Defines a Quality Education. The students in the book traveled to these countries as part of Ripley’s investigation into why some nations consistently outperform others on the PISA. She explores how PISA results are correlated with high standards, teacher quality, and cultural attitudes toward education. Ripley argues that the PISA identifies a kind of educational equity and rigor often missing in the US system. Ripley uses the PISA to expose global education trends and flaws in the American system.

Rigor in education refers to the level of challenge and depth in the learning process and what is required of students to master it. It encompasses high academic standards, critical thinking, problem-solving, and the expectation that all students are capable of understanding complex material. Rigorous education is not, as is commonly thought, defined by volume of work; it instead requires a purposeful and intellectually demanding curriculum, skilled teaching, and a belief in student potential. Rigor encourages perseverance, reasoning, and the ability to apply knowledge creatively.

In The Smartest Kids in the World, rigor is one of the most important factors in What Defines a Quality Education. Ripley identifies it as the main factor that separates high-performing education systems from mediocre ones. In Finland, South Korea, and Poland, rigor is embedded into the entire system, rather than being something reserved for elite schools or top students. Ripley contrasts this with the United States, where high expectations are often inconsistent or dependent on assumptions about the students. Through the lives of three exchange students and their host schools, as well as a host of data, Ripley illustrates how rigor leads to better outcomes. She also warns that without rigor, schools may feel supportive and safe but fail to prepare students for real-world challenges.