Teachers frequently rate boys as more hyperactive/impulsive than girls and Black children more than White children (DuPaul et al., 2016; Miller et al., 2009). Do these ratings reflect true differences in their behavior? Researchers have compared parent and teacher reports (Miller et al., 2009), but is hard to draw conclusions from such comparisons because both parent and teacher reports are subjective. Increasingly, psychologists use wearable sensors to study behavior objectively (de Barbaro, 2019). Given that children's physical movement is a key component of hyperactive/impulsive behavior (Kofler et al., 2020), researchers can assess these behaviors using wearable sensors that detect motion (Koepp et al., 2021). Using an objective measure of children's physical movement, we pursued the following research questions: 1. Do boys and Black children have higher physical activity levels compared to girls and White children? If so, are the magnitudes of difference similar to what teacher and parent reports of children's hyperactivity/impulsivity show? 2. After accounting for children's objectively assessed movement, do parent and teachers rate boys more hyperactive/impulsive than girls and Black children more hyperactive/impulsive than White children? Methods Participants: We used the third-grade wave of the Study of Early Child Care and Youth Development (SECCYD), available from ICPSR (https://www.icpsr.umich.edu). We restricted the sample to children who were White or Black (N = 1,273; Female = 48%, Non-Hispanic White = 86%). Protocol Children wore physical activity monitors around the waist for up five weekdays. Most children had at least four valid wear days (95%; Nader et al., 2008). The monitors recorded the intensity of movement via activity counts that were converted to metabolic equivalent tasks (METs), a unit of energy expenditure equal to that of the body at rest, using the age-specific equation developed by Freedson et al. (1997). Measures Objectively Assessed Movement: We used actigraphy to characterize the frequency and intensity of children's movement (Koepp et al., 2021). We limited the data to periods when children could plausibly be assumed to be at school, during weekdays from 8am to 4pm. We identified periods of high physical activity for each child (i.e., a 30-minute running total of physical activity was one standard deviation higher than that child's regular activity). We excluded these periods from analysis, assuming that they occurred either in recess or in P.E. We then calculated the child's frequency of movement (i.e., the number of times per hour they initiated movement above 3 METs) and the intensity of movement (i.e., their average MET value across the periods observed). As these two dimensions were highly correlated (r = 0.90), we combined them into a single index by standardizing the variables and then taking their mean. Teacher and Parent Ratings of Hyperactivity/Impulsivity: Teachers and parents completed the Disruptive Behavior Index, a measure developed for the SECCYD. We used the hyperactivity/impulsivity subscale. Several of the nine items explicitly incorporated physical movement, for example: "[child] often leaves seat in the classroom or other situations in which remaining seated is expected" and "[child is] often on the go, acts as if driven by a motor" (alphas = 0.85 to 0.93). Results Figure 1 presents mean group differences for boys compared to girls and for Black children compared to White children across study measures. Compared to girls, boys were higher in objectively assessed movement, Hedge's g = 0.37 p < 0.001. Teachers reported a similar difference, g = 0.45, p < 0.001, which was not distinguishable from the difference in children's objectively assessed movement, ?2 (df) = 1.63 (1), p = 0.20. Parents also reported seeing these behaviors more from boys than from girls, g = 0.24, p < 0.001. This was smaller than the difference observed from teachers, ?2 (df) = 7.16 (1), p = 0.008, but was not distinguishable from the difference observed in children's objectively assessed movement, ?2 (df) = 0.66 (1), p = 0.418. Compared to White children, Black children showed greater objectively assessed movement, g = 0.36, p = 0.002. Teachers reported more hyperactivity/impulsivity in Black children compared to White children, g = 0.68, p < 0.001. This was larger than the difference observed in children's objectively assessed movement, ?2 (df) = 4.45 (1), p = 0.035. Parent reports revealed a difference of g = 0.30, p = 0.003. This difference was distinguishable from that observed from the teachers, ?2 (df) = 9.61 (1), p = 0.002, but not from that observed from children's objectively assessed movement, ?2 (df) = 0.14 (1), p = 0.709. Using a path model in Mplus version 8.2 (Muthén & Muthén, 1998-2021), we examined whether children's gender and race predicted behavioral ratings after accounting for maternal education and the children's objectively assessed movement. The path model showed adequate fit, chi-square (df) 885.31 (198), p < 0.001, RMSEA = 0.05, CFI = 0.97, TLI = 0.96, SRMR = 0.05. Children's objectively assessed movement predicted teacher ratings of hyperactivity/impulsivity, ? = 0.25, p < 0.001. After controlling for children's objectively assessed movement, boys were rated by their teachers as more hyperactive/impulsive than girls, ? = 0.20, p < 0.001, and Black children were rated by their teachers as more hyperactive/impulsive than their White peers, ? = 0.16, p < 0.001. Figure 2 shows predicted differences in teacher ratings across levels of frequency and intensity of movement. Children's objectively assessed movement was also a significant predictor of parent ratings of hyperactivity/impulsivity, ? = 0.18, p < 0.001. After controlling for children's objectively assessed movement, parents rated boys as showing more hyperactive/impulsive behaviors than girls, ? = 0.11, p = 0.001, but did not rate Black children as more hyperactive/impulsive compared to White children, ? = 0.04, p = 0.229. Discussion: To estimate the impacts of social-emotional interventions, researchers frequently ask teachers to rate children's behaviors (e.g., Bradshaw et al., 2015; Low et al., 2015). However, teacher ratings are subjective. We wondered whether the differences that teachers report in children's hyperactivity/impulsivity by gender and race would be similar to that observed from parents and an objective measure of children's movement (i.e., actigraphy). Teachers rated boys as showing greater hyperactivity/impulsivity compared to girls. The magnitude of difference was in line with objective differences children's movement. Black children also showed higher levels of movement, though these were not as large as the differences that teachers reported in their hyperactivity/impulsivity. One explanation for this pattern may be racial bias (Okonofua & Eberhardt, 2015). Researchers should account for potential interpersonal biases when using subjective reports of children's behavior.