With growing demand for online courses, it is important to assess the efficacy of quality online virtual instruction. This study investigates the impact of Edmentum's Courseware Algebra I on student achievement using data on 1,205 ninth-grade students from a large urban school district in the Midwest during the 2020-2021 school year. Utilizing a quasi-experimental design, the study compares the NWEA Measures of Academic Progress (MAP) Mathematics scores of students participating in online virtual instruction to those receiving traditional in-person instruction. The study findings reveal that students in the online Algebra I course demonstrated significantly higher mathematics achievement than their peers in in-person classes, with an effect size of 0.13. The positive outcomes associated with Courseware Algebra I highlight its potential as an effective option for high school students.