IPA: /ˌɪn.tərˈskuːl/
KK: /ˈɪntərˌskuːl/
Relating to activities or events that happen between two or more schools.
The interschool competition brought together students from various districts.
Interschool → It is formed from "inter-" (meaning between) and "school" (from Old English "scol", meaning a place of learning). The word "interschool" refers to activities or events that occur between different schools.
Think of activities that happen 'between' ('inter-') different 'schools' — that's what interschool means.