In the past two decades, several major initiatives were launched to improve mathematics and science education. One prominent feature in these efforts was a new approach to teaching mathematics and science, referred to as reform-oriented teaching. Although past studies suggest this approach may improve student achievement, the relationships between reform-oriented pedagogy and achievement were weak. The weak relationships may be partially attributable to the limited time frame in which reform-oriented teaching was examined (typically a 1-year period). This study explored the relationship between mathematics and science achievement and reform-oriented teaching over a 3-year period. Results suggested greater exposure to reform-oriented instruction was generally not significantly associated with higher student achievement but the effects became stronger with prolonged exposure to reform-oriented practices. Reform-oriented instruction showed stronger, positive relationships with open-ended measures than with multiple-choice tests in both mathematics and science and with problem-solving skills than with procedural skills in mathematics. 2009 Aera.