In "Outliers: The Story of Success," Malcolm Gladwell discusses the impact of ability grouping on student performance. He notes that students placed in higher ability groups tend to improve their skills continuously over the years. As they advance, they often gain an advantage that allows them to perform even better in subsequent years, creating a cycle of success and improvement.

Denmark stands out as an exception to this trend due to its national policy of not implementing ability grouping until a later age. This approach suggests a different educational philosophy that may influence student development and success, contrasting sharply with the patterns observed in other countries where early grouping is common.