List one potential threat to internal validity in the article.

Citation:

Aspiranti, Kathleen B., et al. "Classroom management in self-contained classrooms for children with autism: Extending research on the Color Wheel System." Behavior Analysis in Practice, vol. 12, no. 1, 2018, pp. 143-153, https://doi.org/10.1007/s40617-018-0264-6Links to an external site..

Ledford, J. R., & Gast, D. L. (Eds.) (2018). Single case research methodology: Applications in special education and behavioral sciences (3rd ed.). New York, NY: Routledge