To me it reads as if this is unpaired data. Though sampling the elementary schools with at 83% participation rate and the destination high school at an 87% participation rate is sure to cover a LOT of the same students.

> Adolescents in Grades 5–9 at Time 1 and 8–12 at Time 2 completed both self-report and peer nomination questionnaires as part of the larger study. Research assistants visited classrooms to assist in data collection, and all questionnaires were completed on electronic tablets via the online platform Qualtrics. Active parental consent and adolescent assent were required for elementary students (Grades 5–8) while passive consent was used for high school students. In the first wave (November 2019; Grades 5–9), the overall returned consent form rate was 83.78% (including 77.15% positive consent). Students also provided assent to participate; no students who had parental consent chose not to participate. For Wave 2 (November 2022), consent was only collected for the Grade 8s (86.6% returned), and for Grades 9–12, the consent rate was 98% with a participation rate of 87%.

> All measures and procedures received ethical clearance from both the university and school board research ethics boards.

I should also point out that this is from five Ontario schools. Any statements about the behavior of students in other regions would be an extrapolation.