Testing to build research-based evidence to support teaching methodologies that promote student learning has become increasingly important in a standards-based educational system in the United States. One challenge is the lack of studies that support specific methodologies so teachers and administers can make professional development and curricular decisions. This quasi-experimental study investigated the effect of two teaching methods on student content knowledge achievement. Inquiry-based instruction was compared to the subject matter approach in 15 agriscience education classes found within seven different secondary schools across the United States. Utilizing student pretest score as a covariate, there was a statistically significant difference between groups on the posttest. Those students taught through inquiry-based instruction were reported as having higher content knowledge achievement than students taught through the subject matter approach. (Contains 6 tables and 1 figure.)