Many studies show that the instructional materials a teacher selects are critical if they are to have a direct impact on learning (Jackson and Makarin, 2018). They also show that:

• Teachers know that quality materials are essential for student success, but only 18 percent believe that the district-available materials are aligned to standards (Zubrzycki, 2016).
• Overall, students of color and those living in low socioeconomic status areas have less exposure to high-quality instructional materials. 
• Teachers from schools with higher proportions of free and reduced lunch spend more time and energy searching for instructional materials online (Opfer, Kaufman, and Thompson, 2016).
• Instructional materials affect not only student learning, but also the the instructional behaviors and choices teachers make (Chingos and Whitehurst, 2012).

Educators may choose to supplement their established curriculum for a variety of reasons. Research from Polikoff & Silver (2021) shows that adopted curriculum forms a small portion of "enacted curriculum," or what is actually taught to students. Choosing to supplement established curriculum with other resources is usually not a random process. Instead it is influenced by teacher-, school-, and textbook-level characteristics. This suggests that the supplementation process is influenced by structures and policies beyond the individual teacher's control. It is significant thta nearly all teachers source instructional materials online, with 95 percent using Google, 77 percent using Pinterest, and 73 percent using paid sites like Teachers Pay Teachers (Opfer et al., 2016).

Why Use Supplemental Materials?

Using supplemental materials in the classroom can offer benefits such as enhancing learning, motivating students, and providing support for those who need it. Supplemental resources can allow for exploratory learning and provide opportunities for students to explore topics of interest to them. This increases their motivation in subsequent topics in the subject area. They can also help students who might struggle or need additional support. The resources allow these students to see ideas presented in different ways and give them additional opportunities to succeed.

Supplemental resources allow teachers to use proactive and reactive supports that reduce roadblocks to learning. This makes way for them to practice just-in-time teaching and reteaching. Having aligned and engaging materials also lets teachers plan and implement more innovative, effective teaching strategies than may have been possible before.

Used appropriately, these resources can be a powerful tool in motivating, engaging, and supporting students as they work through course elements. In essence, supplemental materials both enrich the learning environment and cater to the diverse learning needs and interests of students. This offers students a more personalized and engaging learning experience​ (Shaw, 2020)​.

The Thomas B. Fordham Institute, in a 2019 study, interviewed teachers about why they turn to online supplemental instructional materials and curriculum. Their responses include:

• Student engagement. Teachers want their students to “buy into content” and  they believe “textbooks are boring.” Some might be looking for fun activities for the beginning and end of the school year. Some might be responding to pushes to introduce new teaching strategies.
• Student needs. They believe supplemental materials that provide enrichment or practice can meet diverse student needs. Teachers say they ”need multiple ways to reach certain students.”
• Instructional effectiveness. Teachers want to fill gaps in content that is making a current curriculum ineffective. Some said that “what I’m doing right now isn’t working.”
• Time savings. Teachers need to find lessons or materials they don't have time to develop for themselves. Some have even grown accustomed to paying for these materials out of their own pockets. One teacher said, “Two dollars is cheaper than two days of my time.”

References

Chingos, M. M., & Whitehurst, G. J. (2012). Choosing blindly: Instructional materials, teacher effectiveness, and the Common Core. Brookings Institution. https://www.brookings.edu/research/choosing-blindly-instructional-materials-teacher-effectiveness-and-the-common-core/

Jackson, C. K., & Makarin, A. (2018). Can Online Off-the-Shelf Lessons Improve Student Outcomes? Evidence from a Field Experiment. American Economic Journal: Economic Policy, 10(3), 226-254.

Opfer, V. D., Kaufman, J. H., & Thompson, L. E. (2016). Implementation of K–12 State Standards for Mathematics and English Language Arts and Literacy: Findings from the American Teacher Panel. Rand Corporation. https://www.rand.org/pubs/research_reports/RR1529-1.html

Polikoff, M. S., & Silver, D. (2021). Identifying and distinguishing among teachers’ supplementary curriculum use patterns using the lasso. In Frontiers in Education (p. 329). Frontiers.

Polikoff, M.S., & Dean, J. (2019, December). The Supplemental-Curriculum Bazaar: Is What's Online Any Good? Thomas B. Fordham Institute. https://fordhaminstitute.org/national/research/supplemental-curriculum-bazaar

Shaw, Adam. (2020, January 31). Using Supplemental Resources in the Online Classroom. Center for Teaching and Learning | Wiley Education Services. https://ctl.wiley.com/using-supplemental-resources-online-classroom/.

Zubrzycki, J. (2016, August 1). Teachers Seek High-Quality Standards-Aligned Curriculum. Education Week. https://www.edweek.org/ew/articles/2016/08/01/most-teachers-see-the-curriculum-in-their.html