skills development using survey data and tracked their GPAs (up to one year post-treatment) via the official administrative school records in the country.<sup>4</sup> <mark>Students exposed to the intervention report improved self-regulation relative to students in the control condition in the academic quarter immediately after the intervention. This improvement comes primarily from the perseverance-of-effort facet of grit. Impacts are larger in the high-intensity treatment than in the lower-intensity treatment. Impacts are larger for female and Roma students, a group that has been traditionally disadvantaged in North Macedonia. Among Roma students, gains in GPAs become stronger over time, reachingup to 28% of a standard deviation one year post-treatment.</mark> The stronger benefits for disadvantaged students echo similar findings in a number of other social-psychological interventions in education (Yeager et al., 2019; Sisk et al., 2018; Paunesku et al., 2015; Cohen et al., 2009; Hulleman and Harackiewicz, 2009; Wilson and Linville, 1982).<sup>5</sup> <mark>While treated students report putting in more effort and being more industrious (i.e. the perseverance-ofeffort facet of grit), they score lower on the consistency-of-interest facet of grit. Thus, a potentially unintended consequence of the intervention is that it diminished interest for long-term goals. One plausible explanation for this result is that by teaching students the value of deliberate practice applied repeatedly to the same stretch goal, the intervention reduced interest in long-term goals – a potentially unintended consequence of deliberate practice itself. This could also be reflective of the intervention not intentionally targeting a specific interest, as well as of the varied interests corresponding to the age of the children participating in the intervention.</mark><sup>6</sup> <mark>It is also worth noting that separate research has shown that developing consistent interests (i.e., specializing) may, paradoxically, depend on diversification (i.e., sampling) of interests earlier in life.</mark><sup>7</sup> To cultivate grit, our intervention followed a two-pronged approach. First, drawing on the evidence on _deliberate practice_ (Ericsson, 2008; Ericsson et al., 1993), students were taught to distinguish effective, evidence-based ways of studying from ineffective ones as well as strategies to implement these more effective ways of studying. Second, we aimed to motivate effort. To do this, we focused on changing students’ beliefs about practice, by raising expectancies and values, two psychological antecedents of motivated, effortful behavior (Pintrich, 2003; Eccles and Wigfield, 2002; Wigfield and Eccles, 2000; Feather, 1982; Crandall, 1969; Battle, 1965; Atkinson, 1957). In Expectancy-Value Theory, expectancy is the extent to which individuals believe they will succeed and, whereby value refers to the subjective value the individual attaches to a positive outcome. The latter increases in expected benefits from effort and decreases in expected costs. Expectancy and value are reliably associated with effort expenditure and achievement, particularly in academic settings (Nagengast et al., 2013; Eccles et al., 1993; Meece et al., 1990; Eccles et al., 1984). We expect students to be more likely to engage in sustained effort if they hold a strong expectancy that doing so would improve achievement, and if they attach a high subjective value to academic achievement. It is important to instill this expectancy – particularly among disadvantaged students – given the prevalence of false, deter-

> 4 The pre-registered analysis plan in the AEA RCT Registry is: Arias et al. (2017). "Can Grit be Taught? Learning from a field experiment with middle school students in FYR Macedonia." https://doi.org/10.1257/rct.2094-1.0.

> 5 Disadvantaged students, whether by income, gender, race, or ethnicity, often experience higher-than-average challenges and stress in academic settings compared to their peers (Schmader, 2010; Beilock et al., 2007; Murphy et al., 2007; Ben-Zeev et al., 2005; Steele and Aronson, 1995). As a result, the decline in grades that is generally true for all students in transition periods (in our case, the start of sixth grade in middle school) is more pronounced for students from disadvantaged backgrounds (Gutman et al., 2003).

> 6 See, for example, Sturman and Zappala-Piemme (2017).

> 7 See, for instance, Gopnik (2020) as well as Cote and Erickson (2015).

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