AimsThe aim of the study was to develop and psychometrically test a new instrument to measure the scope of school nursing practice.DesignMethodological study.MethodsData were collected in Spring 2018. Frontline school nurses in the United States (N = 3099) completed the 39‐item Scope of School Nursing Practice Tool (SSNPT) with two domains (current practice and importance to practice). One half of sample data (N1 = 1521) were used for exploratory factor analysis, item analysis, Cronbach's alpha, and Spearman–Brown to estimate validity and reliability of the instrument. Sample data from the other half (N2 = 1578) were retained for future analysis.ResultsFactor analysis resulted in a stable four‐dimension solution: (A) Using the Nursing Process; (B) Applying Evidence to Improve Practice; (C) Connecting with Community; and (D) Leveraging the School and Family Team, accounting for 50.48% (current practice) and 53.31% (importance to practice) of total variance. Cronbach's alpha and Spearman–Brown ranged from .73 to .90 and .73 to .92, respectively. Item–total correlations ranged from .36 to .82.ConclusionInitial psychometric properties indicate the new SSNPT is valid and reliable to assess the scope of practice of frontline school nurses.ImpactSchool nurses play a key role in population health and frequently serve as the sole provider of healthcare in schools worldwide. However, variability in school nursing practice affects the health, safety and educational outcomes of children and youth. No instrument exists that measures the scope of practice of school nurses. Frontline school nurses can use the SSNPT to assess practice, school nurse administrators can use the tool for resource utilization and school nurse researchers can use the tool to examine school nursing practices’ impact on student/community health and academic outcomes. The SSNPT may provide a template for others who wish to examine specialty nursing scope of practice.