Tools that assess school supports for highly mobile, military-connected students are lacking. This study describes the development and preliminary validation of the Inventory of School Supports-Parent Report (ISS-PR). Participants were 433 parents (74% female; 62.5% White, 12% Black, 6.5% Asian, 5.5% Pacific Islander, 4% Native American, and 9.5% bi/multiracial; 19% Latinx) of students (grades 3-5) from families with an active-duty military parent. Parents completed the ISS-PR and rated: (a) how welcoming schools were toward military-connected families; (b) parent-teacher relationship quality; and (c) satisfaction with their child's school. We created three proportional index composite scores: a 26-item school supports score, a 13-item parent-focused supports score, and a 13-item child-focused supports score. Results supported the ISS-PR's psychometric properties: summary scores were positively linked to parent-teacher relationship quality, school welcoming, and parent satisfaction with the school. We also found evidence for test-retest reliability for parents completing the inventory with students who had either moved schools or remained in their previous schools. Future studies could use the ISS-PR to assess whether parents' perceptions of the availability and importance of school supports for military-connected families are related to other constructs such as overall school climate, student academic performance, and socioemotional functioning. Schools could use the inventory to determine which supports could potentially have the greatest impact for military-connected families and to what extent parents are aware of the supports schools offer.