Mathematics education is important for students with developmental disabilities. Additional research is needed that examines interventions to teach grade-level mathematics content to these students. In this single-case multiple probe across participants study, researchers explored the functional relation for four middle school students with intellectual disability and autism between the intervention package of a virtual number line and corrective feedback and solving addition of integer problems. Students solved more problems correctly with access to the virtual number line in comparison to baseline. They also maintained higher levels of accuracy during the maintenance probes when corrective feedback was withdrawn. Implications from this research include the option of a virtual number line as a potential intervention to teach secondary students with developmental disabilities grade-level mathematics content.