Teacher-student relationship quality (TSRQ) predicts academic motivation (Wentzel, 1997), school engagement, and academic achievement (Hughes, 2011). However, TSRQ appears to differ across demographics. For example, boys and racially/ethnically minoritized students consistently have poorer relationships with their teachers than girls and White students (Koomen & Jellesma, 2015; Murray et al., 2008). Ensuring that TSRQ is consistently conceptualized across individuals will allow demographic differences on TSRQ to be compared. The present study aims to further validate a survey instrument used to measure TSRQ, called the Inventory of Teacher-Student Relationships (IT-SR; Murray & Zvoch, 2011). Participants included 3,541 middle and high school students in a large school district in the Southeastern United States. The results of the study confirmed the hypothesized three-factor structure of the instrument. The instrument demonstrated configural, metric, and scalar invariance across race/ethnicity (Black/African American, White, Hispanic/Latinx, and multiracial) and partial metric and scalar invariance across gender (boys and girls) and school level (middle school and high school). Significant latent mean differences were found, where boys, Black/African American students, Hispanic/Latinx students, and high school students reported lower scores on various factors on the IT-SR compared to girls, White students, multiracial students, and middle school students, respectively. Results support future research and applied use of the IT-SR with middle and high school students. (PsycInfo Database Record (c) 2024 APA, all rights reserved).