Purpose: The purpose of this study was to establish a line of inquiry into student trust in school peers by--(1) developing a valid and reliable measure and (2) investigating the potential influence of student trust in school peers on optimal school functioning. Design/methodology/approach: A non-experimental, survey research design was used. Ex-post facto data were collected in the spring of 2017 and spring of 2019 from a random sample of students in either the 5th, 7th, 9th or 11th grades in 79 schools located in a southwestern city in the US. Two types of analyses were performed. First, structural and convergent validity of the items measuring student trust in school peers were tested with a confirmatory factor analysis, and correlations with bullying and safety. The second analysis tested a hypothesized model with a full structural equation model using robust maximum likelihood estimation. Findings: Confirmatory factor analysis results report that items used to measure student trust in school peers share common variance with the latent trust factor. Both the 10-item and five-item measures had good model fit and parameter estimates. Additionally, the five-item measure had strong relationships with bullying and safety. As specified in the hypothesized model, student trust in peers had a strong, positive relationship with identification with school and positive, yet not as strong, of a relationship with academic grit. These relationships existed when accounting for student perceived teacher support. Originality/value: This study extends trust research to students' relational connections by conceptualizing student trust in school peers as a cognitive belief, constructing a valid measure and finding a relationship between student--peer trust and elements optimal school functioning.