the remaining LIWC categories, there were no significant long-term differences. Because these findings were not predicted and several did not reach the conventional threshold for statistical significance, they should be interpreted cautiously. Table S1. Effectiveness of Random Assignment in Study 2: Non-Significant Pre-Intervention Differences Between Conditions Control Experimental Preintervention variable Test statistic = M M p % Female 46% 54% = 0.46 .50 χ2(1) % White 54% 41% = 2.65 .27 χ2(1) % Latino 5% 14% = 1.69 .19 χ2(1) % Mother has a college degree 72% 73% = 4.71 .45 χ2(1) % English is the primary language spoken in the home 67% 63% = 0.09 .77 χ2(1) Average 8th grade achievement1 2.82 2.83 = 0.07 .94 t(76) Entity theory of personality 2.56 2.8 = 1.03 .31 t(76) Frequency of peer exclusion/victimization4 2.16 1.95 = 1.02 .31 t(76) 37 41 N 1To gain precision, preintervention achievement is an average of grade 8 Math/English grade point average and Math/English California Standards Test scores (the latter was re-scaled to have same mean and standard deviation as grade 8 grade point average). Table S2. Effectiveness of Random Assignment in Study 3: Non-Significant Pre-Intervention Differences Between Conditions Control Experimental Preintervention variable Test statistic = p M M % Female 51% 47% = 0.16 .69 χ2(1) % White 5% 10% = 1.27 .25 χ2(1) % Latino 79% 79% = .005 .94 χ2(1) % English is the primary language 40% 38% = 0.04 .83 χ2(1) spoken in the home Average 8th grade achievement1 1.82 1.82 = 0.08 .94 t(153) Among baseline entity theorists 1.68 1.70 = 0.13 .90 t(45) (>3.5 on entity theory scale) Among baseline incremental 1.92 1.93 = 0.16 .88 t(102) theorists on entity theory (≤3.5
the remaining LIWC categories, there were no significant long-term differences. Because these findings were not predicted and several did not reach the conventional threshold for statistical significance, they should be interpreted cautiously. Table S1. Effectiveness of Random Assignment in Study 2: Non-Significant Pre-Intervention Differences Between Conditions Preintervention variable Control M Experimental M Test statistic p = % Female 46% 54% χ2(1) = 0.46 .50 % White 54% 41% χ2(1) = 2.65 .27 % Latino 5% 14% χ2(1) = 1.69 .19 % Mother has a college degree 72% 73% χ2(1) = 4.71 .45 % English is the primary language spoken in the home 67% 63% χ2(1) = 0.09 .77 Average 8th grade achievement1 2.82 2.83 t(76) = 0.07 .94 Entity theory of personality 2.56 2.8 t(76) = 1.03 .31 Frequency of peer exclusion/victimization4 2.16 1.95 t(76) = 1.02 .31 N 37 41 1To gain precision, preintervention achievement is an average of grade 8 Math/English grade point average and Math/English California Standards Test scores (the latter was re-scaled to have same mean and standard deviation as grade 8 grade point average). Table S2. Effectiveness of Random Assignment in Study 3: Non-Significant Pre-Intervention Differences Between Conditions Preintervention variable Control M Experimental M Test statistic p = % Female 51% 47% χ2(1) = 0.16 .69 % White 5% 10% χ2(1) = 1.27 .25 % Latino 79% 79% χ2(1) = .005 .94 % English is the primary language spoken in the home 40% 38% χ2(1) = 0.04 .83 Average 8th grade achievement1 1.82 1.82 t(153) = 0.08 .94 Among baseline entity theorists (>3.5 on entity theory scale) 1.68 1.70 t(45) = 0.13 .90 Among baseline incremental theorists (≤3.5 on entity theory 1.92 1.93 t(102) = 0.16 .88