Researchers established virtual manipulatives as an evidence-based practice for students with intellectual and developmental disabilities (IDD). However, much of the existing research for this population targets middle school students with IDD. This study examined a virtual number line paired with teacher modeling and the system of least prompts to support high school students with IDD in acquiring, maintaining, and generalizing addition and subtraction problems. Through a single case research study with three high school students with IDD, the researchers found a functional relation between the intervention package and student accuracy. Students also became more independent but struggled to maintain their skills when prompting was not provided. Further, the students were unable to generalize the skills of addition and subtraction to real-life scenarios targeting time and money. These findings and their implications for the field of IDD are examined.