“…This expectation is based on findings by Fuchs, Fuchs et al (2015), who found that, across three years of intervention research, the achievement gap on fractions performance widened between at-risk students and their not-at-risk classmates in the same district where the present study took place moved toward implementation of CCSS. This widening gap is likely due to the rigor of CCSS, affording greater learning outcomes for not-at-risk students, even as it posed specific difficulty for at-risk students who already struggle with foundational skills (Powell, Fuchs, & Fuchs, 2013). Specifically, low performing students tend to struggle with magnitude estimation (e.g., Fuchs et al, 2013; Fuchs, Fuchs et al, 2015; Mazzocco & Devlin, 2008), a core tenet of fraction learning outlined in the CCSS.…”