Policymakers often rely on simple quantitative indicators to navigate complex policy environments, yet these indicators frequently become targets that distort the very processes they are meant to monitor. Drawing on Campbell's Law ( 1979)) and two cognitive biases—availability heuristic and attribute substitution—this interpretive case study of Quebec's education policy examines the consequences of elevating the high-school graduation rate to the central performance target. Since the 2017 Politique de la réussite éducative, education spending has risen by 55% (2018–2019 to 2024–2025), the graduation rate has increased from 71.9% to 82.4% (2023–2024), and pass rates on ministerial examinations have improved. However, Quebec's scores on the Programme for International Student Assessment (PISA) in mathematics, science, and reading have stagnated or declined over the same period. The analysis identifies rational institutional adaptations—such as the rapid expansion of students designated with handicaps or learning difficulties, widespread use of assistive technologies in assessments, and teaching to the test—as mechanisms that boost the visible indicator without corresponding gains in deeper cognitive competencies. This case illustrates how cognitive biases and reductionist heuristics in governance can produce an illusion of progress, underscoring the need for decision-making frameworks that incorporate independent external benchmarks to better align incentives with genuine student competency development.