1.
this school; our school
The way a school refers to itself in formal writing and announcements. Used by the institution about itself, never by an outsider talking about someone else's school.
The prefix 当 ('this, the present one') is how an organization refers to itself in formal Japanese: 当社 (our company), 当店 (our shop), 当院 (our hospital or clinic), 当館 (our hotel or museum).